Do you know what is it yet? I think that's part of the reason I'd fear doing weight exercises some time ago. I had access to a gym from my brother's apartment though I wouldn't follow instructions too much, which can have bad consequences. Maybe you overdid it bouncing for too much time? I know that when I used to run for a hour or so my knee started hurting when I was 40 minutes and it still bothers me in the 40 minutes time, though not as much as before, since I'm doing gym with a set of exercises with a closer follow up, which is also needed since boxing uses too much the legs and I'd also notice my knee bothering me after I was moving for a while. I think maybe looking at ways to strengthen it with professional help in a gym is better than doing some activities on our own that may force it more than it's currently prepared to take.