It's most likely one of those. If I were to guess, I would say it's Chondromalacia patella which is a common cause of kneecap pain or anterior knee pain. Often called "Runner's Knee," this condition often affects young, otherwise healthy athletes.
Chondromalacia is due to an irritation of the undersurface of the kneecap. The undersurface of the kneecap, or patella, is covered with a layer of smooth cartilage. This cartilage normally glides effortlessly across the knee during bending of the joint. However, in some individuals, the kneecap tends to rub against one side of the knee joint, and the cartilage surface become irritated, and knee pain is the result. http://orthopedics.about.com/cs/pate...dromalacia.htm
I experienced pain a while ago in my right knee after playing bball for 7 days straight. I couldn't bend my knee very far or move laterally without pain. I rested for a couple weeks and it went away. I started doing the VJB and it came back a little so I bought some knee brace things. I just went to CVS Pharmacy and bought them for 20 bucks (each) and they have made a big difference. Put it this way, I couldn't play for an extended period of time without them. If I were you, I would rest for a while, then buy yourself some of these. You can wear a sleeve as well and then put the brace over it that would probably work really well tho might be a little overkill.
Be sure when you do weight training not to go down past parallel though on exercises like squats, that will only screw it up even more. Wait until you don't have any pain to start weight training too. Resting sucks when you want to play... but you just have to.