For those who have bumps at the incision after circumcision, it is considered to be caused by scar formation, improper surgical operation or rejection reaction. 1. Scar formation: after circumcision, scar healing may occur at the incision, and scarring will lead to local tissue bulging or depression, contraction and other phenomena, which may lead to bumps at the incision. 2. Improper surgical operation: If the layers of the two incisions are not completely aligned when they are sutured together after surgery, one side will be higher than the other, resulting in bumps protruding from the skin. 3. Rejection reaction: the thread or anastomosis used for surgical suture is a foreign substance to the body, and when the body rejects it, it may lead to local tissue hyperplasia, and then bumps appear on the incision.