Something is wrong with my knee?

About a year ago, I fell and skid right under my knee... it really hurt and I hit some kind of nerve. Like I said, that was a year ago. My knee has given me a bit of trouble over that time period, but now it's starting to get a little worse. I don't recall re-hitting it recently, but maybe I have... I would like to know what's wrong? When it does hurt, there's this really...strange feeling. It feels compressed in a certain area, and it kind of feels like it's moving? It hurts and feels weird at the same time, so the feeling is indescribable.. But! I would like to know if anyone knows what exactly is wrong and what I should do. Thanks :3