Thanks for posting your query
I dont think it is of much concerned. You will worry much and consult doctor
if the followings are present -
1. constant persisting pain over that area
2. discharge from the incision site
In these cases you should consult your surgeon and usg scan if needed should also be done.
As already 3 weeks have already passed i think the punch will not cause much damage.
Meanwhile you should continue post-op antibiotics, dressing of the wound, nutritious diet.
You should also do some abdominal muscle wall strengthening exercises.