When I had my appendix removed, the skin around the incision was numb, entirely numb to the touch so I could not even really tell that I was touching my own skin. I asked the doctor about it and he said, "Oh, they probably cut a skin nerve. It's no big deal, it will heal in a year or two." (!) I would have thought (at that time) that something that wouldn't heal for a year or two *was* a big deal, but the doc really just shrugged it off. And guess what, it did heal in a year or two. The area of the skin that was numb slowly got smaller, and now it just feels normal. Maybe something similar is happening to you. Ask your doctor, for sure.
You were diagnosed with testicular torsion for why they did the orchiopexy surgery? https://my.clevelandclinic.org/health/treatments/17297-orchiopexy Oh, I see. It was to descend one testicle. I'm surprised they didn't do that when you were young when it is more commonly done. It's important to let yourself heal after that surgery! I would guess given some time, this will probably resolve. Trauma, injury are two reasons for numbness. I would guess that nerve compression is the likely culprit though. Nerve compression or damage. If your situation continues, see your doctor for follow up. Not the ER per se but your regular doctor.