Rib injury question

Patient: I suffered a rib contusion (the x-ray showed no actual break) during a football game almost three months ago (no pads, it was a pick up game). While I had some significant pain for the following weeks, for the most part I have healed. However, I still have some soreness or discomfort in that area, especially after running, swimming or working out. Everything I read and have been told is that 4-6 weeks and I should be completely healed, but I still feel some soreness 12 weeks later. Is there a reason why?

Symptoms: Soreness/discomfort of the injured rib, usually after a workout.