What you have done so far is good. I'm not expert but I would say wash the wound with a little bit of bottled water if it looks dirty. Keep him on paper towel with just a hide and shallow water dish. I'm not sure about medications as such, or even if there are any but I experienced a sick sal.
My wee guy had a small wound on the inside of his thigh which then turned into a hole. He became very dull and wasn't eating as he did previously. His skin sloughed off his leg, and I could see right through his leg
I honestly thought either he was going to die or lose his leg. I kept him in a small tub with damp paper towel, 1 hide and a shallow water dish. Kept him cool and in a quiet room and fed him every 2 days as much as he would take. Checked on him everyday and sure enough about 3ish months later the leg was healing, the hole had gone and he became his old self
It's astonishing how these amazing little creatures can heal themselves!
I would just advise getting as much help and info from the lovely people on here and keep him cool, calm and in a sterile environment. And don't give up hoping
Fingers crossed for you and the wee one!