Hard to tell by the photo, but at least the rest of the foot looks all right- not scaled or bumpy with mites or anything, at least not on the leg/foot. Unfortunately that rules out scaly mites, which are fairly easy to treat for.
I can't tell if there's any claw left on the damaged digit (can see the back claw is healing nicely), but if there's NOT claw on that front digit, if all that red is skin, it looks inflamed/infected. Are you able to keep him separated from the other birds and keep him on dry, clean ground for a few days? Keeping that wound dry and clean is most important. I am not sure what caused this, but if it happens again I would recommend taking him to a vet if you can. Check your yard for places where he might have snagged a toe, and keep cleaning and applying neosporin.