My husband has swelling and pain from hernia repair in December. Right testicle completely numb since surgery.

6 months is too long. Numbness below a hernia incision is not unusual and results from the skin nerves being cut. This may be permanent, but should not affect any functional activity. Pain and swelling 6 months after surgery is too long and should be evaluated by the surgeon. Sometimes this is due to something simple like a blood clot or a healing reaction and may get better with heat and ibuprofen, but it should seen.