I have personal experience with ankle and heel problems - much more so than I'd like. It's bad to the point where any time I've been sitting for 5 minutes then stand up to walk, it can be painful. Seeing me try to walk first thing in the morning is quite a comical sight. Specifically in my case, the problem spots are in the Achilles tendon just above where it connects to the heel, right behind the ankle. This is often a problem point, since this tendon carries the entire body weight with every step. Add to this running and jumping, especially on a hard surface such as the (literally) rock-hard surface such as MIT (a local dance place, also a technical trade school you may have heard of), and you're putting a lot of use/abuse on your system. Women are more at risk for this type of injury since they often wear tight fitting shoes that press in on this spot, resulting in an inflammation called a "pump bump". I had this for a while (no snickering, please) from wearing very close fitting sneakers and dance shoes for dancing. A change in footwear and some orthotics helped, but the remnants of the condition endure.
So much for personal experience on this area in specific; let me give you some general info that all dancers should know. It's common knowledge that before engaging in any strenuous physical activity one should "warm up". What's amazingly little-known is how to do this. The common perception is to walk into the room, take off your coat, and start bending and twisting this way and that, stretching here and bouncing there, pushing and pulling and doing all manner of things that we see "real dancers" doing. Well, OK, but not yet. "Warm-up" means warm up. Stretching comes later.
Think of muscles as rubber bands. It's really a pretty good analogy: they create motion by pulling, the larger ones can pull harder than the smaller ones, and the range over which they can pull is related to how far they can stretch. In the case of a person, we're also concerned with flexibility, or how far a muscle can be stretched (such as how high the leg will go) without being interested in the pull back. If you've got a rubber band lying around, get it now and we'll do this with props. (I'll wait for you to find one.) Let's say you're now holding a rubber band. This is your muscle/tendon. Stretch it and feel how much resistance it gives you. Now bunch it up in a little ball and roll it between your palms for a minute or so like you're rolling a ball of cookie dough. Feel it getting warmer? THAT'S a warm up! Now try stretching the rubber band and notice the resistance. Less, yes? You can stretch it farther easier. Same with muscles.
For the next part of the experiment you'll need a refrigerator, so if you don't have one handy you'll have to trust me and work from experience and common sense.
So now let's take that same rubber band and stick in the freezer for about 20 minutes and get it nice and cold. Then take it out and try to stretch it; what happens? One of 2 things: either it won't stretch as far as when it's warm, or it snaps altogether. Again, same with your muscles. And since the muscle is the more pliable of the muscle / tendon pair, it has more give to it and it's often the tendon which suffers for the sins of the muscle (excuse the image, but you get the idea).
When you walk in the door at dancing, your muscles (and the tendons attached to them) are cold and they need to be warmed up. Yes, stretching helps and benefits you in the long run, but just as you must warm up that rubber band before you can stretch it out without hurting it, you need to warm up your muscles before you stretch them to avoid hurting YOU. Once you're warmed up you may stretch. (Ideally the best time to stretch, giving you the best long term results, is at the very end of dancing when your muscles are the warmest. Unfortunately, that's when most people just go home.)
How to warm up? The absolute best way to warm up any muscle is to use it normally. In the case of muscles of locomotion that means walking. Park far enough away that you have to walk a few minutes to get in the door. Once you're there, walk around the room, maybe jog or run a little bit. Or bounce up and down in place lightly (not a stretch bounce, pushing against a wall or otherwise changing the normal geometry of the foot and leg). This is actually a layman's version of what every ballet class for hundreds of years has always started with: plies and releves. In fact, in all dance classes (or at least all good dance classes) the warm-ups come first and the stretching comes later. By the way, if you sometimes see professional dancers start off their warm-ups by flopping over in half and "stretching", keep in mind that what's a normal range of motion for them isn't the same as normal for you and me, and that they too will warm-up before exceeding their normal zone.
Now what to do once the inevitable happens and you've hurt yourself. The several standard care steps are rest, ice, compression, elevation (or RICE, to the jargon acronym oriented). Simply put: stay off it as much as possible, apply ice (or other cold things: a bag of frozen peas is great) after use to prevent swelling, use ACE bandages, and sit with your feet up (again, it keeps the fluid out and prevents swelling, besides being relaxing). Motrin or other ibuprofen drugs also help with muscles pain and swelling; I often take one or two a little bit before dancing as a preventative measure. After the immediate care period, such as the next day, you may replace the ice with warmth to make it feel better.
So here's the summary: Prevent muscle and tendon injury by wearing appropriate attire (footwear specifically, but also think about leg warmers or at least long pants), begin each session of activity by first warming up, work your way up to the maximum level of structural stress and exertion, end by cooling down (a great time to do your stretching to extend your baseline range of motion), and apply any care afterwards as may be needed to treat any injury or pain which you may be experiencing. With this done at least most of the time, you should be able to go on having a good time for a long time. (So why, if I'm so smart, do I hurt? Because like most people, even when I know what's the right thing to do, I just jump in and don't do the basic preparations. Also in my case since I run the music at a lot of dance things, it's very much stop and start, back and forth throughout the evening, so I go through many stop / go periods without the proper warm-up / cool-down cycles as I should, and I suffer for it.)
My qualifications for being so pedantic, I'll add here, come from more than just personal experience. I'm the proud owner of a BS ED in Dance, which means that I studied dance from an educational as well as artistic perspective. Things such as injuries and physiology were as central to the program as the correct way to pirouette. (I actually got graded on taping an ankle and applying ACE bandages, straight A's there. And I do that better than I pirouette, let me tell you.) Folk dance doesn't place the kinds of strain on the body in general as some other dance forms do, but it places extreme stresses on certain parts, especially feet, ankles, and knees. It also almost never gives good background information on how to prepare against or treat for injury, and that's a shame.
I see that I've really rambled on here, but it's a pet peeve of mine when people get hurt / stay hurt because of things they simply didn't know or knew wrong or otherwise could have been prevented. I hope this helps you.
(Note: this was originally written as a piece of friendly advice for someone at a local dance session, and she made the suggestion that I make it more widely available. Thanks, Jenna.)