My leg hurts, what's wrong?

My name is Justin, I'm 15 yrs. old my day consists of walking up and down stairs at high school, getting to time on classes, I have a trampoline but have not jumped on it lately, things I think might have happened: I sometimes skip the steps on my porch but haven't done that either lately and during study hall I put my leg under my but or fold them on top of one another or put them under the table and have them set on the seat in front of me while I'm reading. I also run, but do not go out for any sports. Other than this I have no clue, my immune system is fine, I'm fine, haven't done anyhting different lately, It's 8:40 p.m. here, I get out of school at 3, so anyways a couple hours after school is when I got the pain in my right leg, I get the pain by my knee when I take a hold of my foot and bend it towards my butt is when it starts to hurt, what could be wrong with it? I am normal, you know don't get sick very often, am active, skinny, and flexibility is an 8, so what's wrong??ThankMy leg hurts, what's wrong?
Sounds like you can have some bone spurs possibly in your leg. Or you could be going through growing pains as well. Or even your body is lacking potassium, eat a bannana and see if that helps with the potassium loss. If not keep your leg elevated and treat it as if it were a sprain with ice/heat. You are doing the right thing by taking some anti-inflamatory pills. However, if it doesn't improve with in a day or so it would be wise to seek some medical advise.
I broke my leg 5 years ago, and whenever I am running for a really long time, it does this really weird thing. It feels like there is an air bubble in my hip. It stays there for a couple of days, but then it goes away.
I just try not to run a lot.
[i hope this helps you!]