Hi, my job largely consists of dealing with Pig that have ringers, whilst i wouldn't diagnose, this doesnt look like typical ringworm. Is the skin white and patch or flaky at all around the area, and is there any other signs of spread around the body?. By the looks of the wound it looks as if it has been bitten, as the wound looks like an upper and lower bite. Personally, id recommend taking to a vet just to be on the safe side but if not, then treat it at home with some cooled boiled kettle water and salt or hibi scrub diluted. Also keep any eye out for any dominant behaviours exhibited by your other piggos! goodluck!