Hi S.,
I had my emergency C-section in 9/07 and I am still lumpy and sore sometimes. I just went back to the doctor to discuss it again. She said that it takes time, could be near the bone, internal stitching, etc. They really don't know. She also checked for a possible hernia and is now checking for infection too.
Don't want to alarm you but wanted to let you know those possibilities. So if it is uncomfortable, especially when "playing tennis" you might want to consider going back to the Doctor and not just waiting.
I am sure you are fine but always good to have peace of mind......... I'm still looking for it. ;)