Black & Blue from Inguinal Hernia

FYI:Men: In men, the scrotum or penis may become bruised (black and blue) or swollen. The swelling, if it occurs, can become large. This represents that the space where your hernia once was has filled with fluid. This is usually from something called a seroma. If this is happening, there is nothing specific that needs to be done other than sometimes holding compression (or wearing a binder) can minimize the swelling. Make sure to notify your surgeon and show him this. Over time, in most situations, this will resolve completely spontaneously.

http://www.nychernia.com/for-patients/inguinal-hernia-surgery-discharge-instructions/