Soreness suddenly 2-3 months after scar injection

[nyce]

I am 2 years post-op.  A few months back I went in for a last check up and decided with one side having a little scaring at the incision point to have the scar treated with an a steroid injection.

There was no pain experienced then or up until today and the scaring has reduced to almost nothing as a result of the inject..  Just this evening, however, I started noticing tenderness/soreness and some mild swelling around where the injections were administered. 

I plan to contact my doctor tomorrow morning, but in the mean time is this reason for concern?