It's pretty much impossible to tell just by looking at something if there's a sprain, a fracture or a broken bone. Often times we roll our ankles. We overuse our arms. We overuse our wrists. It's usually the joints that you feel this in if you have a sprain. Something like that. Take a load off of it. Especially if it's your feet, sit down. Or if it's your arm, don't do the same motions again. Ice it. Give it some ice and see if that'll help with the swelling. If it's more than just sore, you're going to want to worry more about fracturing or breaking. It's really impossible to tell just by looking at it. Sometimes you can tell, you can get hints if your bones are misshapen. If you're hearing funny noises when you use your joints. If you lose sensation, if you get numbness or tingling or things feel hot or cold when they shouldn't. Anything that feels different or strange, you really need to check it out with your doctor. The only way to really tell is an x-ray. Fractures can seem like they're nothing. They can seem like something you can just tough out, walk through, walk it off, run it off, you'll be fine. Muscle through it. But, it really can cause further damage if you don't get it taken care of right away. You can cause further fracturing. You can cause a break. You can damage the surrounding tissues, and nerves and tendons. So, if you even suspect you have a fracture, don't try to tough it out. Go to a doctor. Get it checked out. Get an x-ray and be certain 100% that you're not going to cause further damage.