What is the lump in my groin area after hernia surgery?

Probably : Healing ridge, but check with your surgeon just to make sure that it is not hematoma or deep infection.

Proud ridge: Shortly after surgery, scar tissue forms wherever a dissection occurred. In the early stages, the collagen laid down is unorganized and contains fluid. This leads to a firm narrow mass under the incision and down the inguinal canal. As the scar matures, the ridge flattens out. This takes about four months.

Seroma: It is likely a fluid collection in the space the hernia once occupied. It will resolve over 4 to 6 weeks.