I would say its a small rip or tare from over use. You seem to train quite frequently. It is good to do so, but all the jumping in parkour is very taxing for the legs, so it's not always a good idea to be doing so much leg conditioning all the time. Sometimes the running and jumping found when practicing techniques is a lot of conditioning on its own, so when you pile on hundreds of squats and other things it can slowly cause problems like small rips or tares. A doctor will most likely just tell you to rest, so I'll save you the trip and just tell you the same thing. Rest up! Don't practice any...