If this pain is getting worse and your son isn't getting a relief from the prescribed pain killers you should notify his surgeon.
Pain or discomfort that is experienced as burning sensation at the incision site, is suggestive for pain with nerve origin.
The nerve injury is a complication of hernia repair and could be attributed either to direct surgical trauma or to delayed injury caused by postoperative inflammatory changes.
This nerve injury is manifested as chronic pain after hernia repair (felt years after the surgery) and the cause is usually corrected with intervention.


Best wishes!