does He cruise along the glass? Mine does and he gets a sore at the corner of his lip... Melafix does the trick... and a quick cleaning of the glass seems to help prevent it from happening again In my case... Buster seems to stick to the glass in some spots ... not sure why but he seems to enjoy himself with it LOL
Most likly it is from tankmates...it usually heals up just fine keep up on your water changes and add some Melafix and it'll help speed up the process alittle