Lump under my skin...please help!?

About 4 inches below my knee and 4 inches above my ankle there is a lump under my skin. It's slightly noticeable when I stand up, not noticeable at all if I lay down or sit down, but if I move my leg close to my body (kind of like fetal position) it is quite noticeable. There is no redness. It doesn't hurt. When I put my finger over the bump that sticks out about a centimeter or two, I feel a sort of squishing. I wonder if it may be a tendon or something that is injured? I'm really scared because I don't play sports, so it can't be from sports related activity. Also, I'm a 17-year-old female, if that helps. I read about something kind of similar called "Osgood Schlatter Condition." It sounds kind of similar to that, but I don't know.