You are probably reacting to something you are putting on your skin, either a cream or adhesive. Check with your surgeon. Switch to something mild like Dove soap and an over the counter steroid. Should clear up in a couple weeks.
Sensitivity to adhesive is the most common cause of a bumpy and itchy rash around an incision right after surgery. You can wash the area well with Ivory soap, and apply an over the counter steroid cream for relief, though it is important to check with your surgeon before you do so.