What's wrong with my leg?

Since I got home tonight (about 8 hours ago) the muscle on the inside of my left leg just above the knee about an inch has been twitching. Every few seconds it just tenses up. It doesn't hurt but it is really freaking annoying. Doesn't matter if my leg is straight or bent or even if I'm standing. I took a nap for awhile but as soon as I woke up it started happening again (not sure about during the nap because, umm, well I was sleeping). There have been stretches of a few minutes when it wouldn't do it but it has always started up again. I punched it once to make it stop, yeah that wasn't a good plan. Then it hurt and twitched (note to self punching your self is bad umm kay). I have no idea what caused it to happen, why it is or how to make it stop. If anyone has any ideas or wants to make up something I'd love to hear read them. I'm willing to try pretty much anything (I punched myself) to make it stop before it drives me completely insane. I'm going to go do some yoga to see if that will help at all.