talk to your surgeon but it is not unusual to have some leakage of blood under the skin or subcutaneous tissue "south" of the surgical incision that could involve the penis or scrotal area. blame it on gravity. this would look like a deep bruise. it may be red af first but then turns a bluish-purple as the body reabsorbs the blood.
hernia surgery dark redness in penis shaft. looks like blood build up? no pain and incision area looks clean and well.