It could be an infection or it could be that he's been hurt by the other male
Cuts and scrapes should always get cleaned up straight away and given a quick spray of antibiotic spray (like Teramycin) to stop infection setting in
You'll probably need to give a jab of antibiotics for the infection. Acting quickly in the first instance saves a lot of trouble in the long run
What age is he ? and what age is the other male ?
I would NEVER recommend mixing uncastrated males, ESPECIALLY when there is a female in the mix. Uncastrated male pigs will fight (sometimes with fatal consequences) and having a female present will make it much worse. You need to seperate them
straight away and have one or both castrated as a matter of urgency if you want them to mix.
I'd seperate out the one who's not quite himself and keep him on his own til he's recovered and back to his usual happy self, don't mix him til you sort out the castration issue.
HTH
Karen