First, find out exactly what's broken (if possible).
Second, how long ago did you screw it up? Rehab is always most effective shortly after an injury. I ruptured the ACL in my right leg a couple of years ago while playing basketball
(some dip**** former tailback for the Canadian football league basically tackled me as I was headed to the bucket on a fastbreak). I had the ACL replaced/rebuilt using a borrowed and reworked hamstring tendon (from same leg). Rehab was a bitch. I couldn't bend my knee—and I couldn't straighten it either.
Over the course of about six weeks, I very slowly (and painfully)stretched it into shape. Because I made the effort then, I now have full range of motion. In fact, my right knee is in better shape than my older (loose from 30 years of basketball) left knee. The orthropaedic surgeon and the PTs let me know from the get-go that if I didn't work intensely on flexibility (shortly after the operation), then the newly placed tissue would always be tight.
I'm not a doctor, and I'm not recommending that you stretch the hell out of it (like I did mine), but I would recommend that you see a doctor with substantial experience in treating sports injuries. There are plenty of doctors who don't know diddley.
If you want, I can tell you exactly
what I did to encourage flexibility, but I don't know whether it would do you good or harm.