Have you checked for lice or mites? It is possible that he might have a fungal infection called favus. If there are no mites or lice, you could try applying an antifungal cream daily. Clotrimazole can be found at Dollar Tree for $1, and you can also use Miconazole or Monistat.
One other possibility is that he is getting feather picked by his flock. I don’t know about the swelling. That can sometimes be from a sinus infection and respiratory disease. Does he have any sneezing or nasal drainage, or any gunk in his eyes? Would it be possible to get some pictures a little farther back to show his whole head?