I had a boa that an IDIOT snakesitting for me did 'help' shed way too early that was swollen in the same way but MUCH worse when I got home. If hes still looking ify rub some neosporin on it each day and it should clear up. I raised my boa's humidity as well but unless you run a fungus preventative that might be a little iffy given its an open wound and on the belly where scale rot typically attacks. On a side note it took my boa about 2 sheds before he started looking normal again, and he was REALLY jacked up from it to the point of loosing scales so the white underneath was visible.