Pain at incision point

by Ivano
(Montreal, Canada)

Four years ago I had ACL surgery (hamstring graft)after a soccer injury.
I waited about 2 months before starting physiotherapy. After physio, I then joined a gym (as was recommended to me) to do cycling and some weight training (not excessive). I did not even attempt to play soccer for another year and half (due to work and to allow it to heal).
When I did start playing, after a few games, I felt light pain below the knee right where the incision is, so I immediately stopped.

Being in Canada, I had to wait another 5 months to see my knee specialist surgeon. He looked at my knee and said it was solid, so the pain may simply be the attachment that had yet dissolved or been absorbed. (As I understood, the manufacturer's estimate was rather optimistic and it may take longer.)

I again stopped soccer and returned to simply cycling, skating and weight training to stay active and only rarely felt light pain/annoyance at the knee.

A few weeks ago, I started soccer again. The pain is back and is really pretty strong to the point where I limp when using stairs (but not walking or skating?). Looking at the incision/scar point, I see there is a slight bump.
I will request an appointment with my surgeon (but it will take a few months) but can you provide any insight as to what this might be?