That looks like a pretty classic and mild case of fowl pox. A nuisance virus, but nothing to worry about. You can swab some straight betadine/iodine on the nodules to help dry them out and prevent secondary infection, but it is not necessary. Fowl pox usually heals on its own without intervention in about 3 weeks. It looks nasty, but is relatively harmless.
Good luck.
ETA- Old thread. That bird is long healed.
luckyrooster- The way to tell if scabs are pox or picking is to look at them. If they are raised like nodules then they are pox. If they are just flat black scabs then they are due to picking. The bird in the pic has obviously nodule-like projections under the black, ergo fowl pox. Black scabs present without the growths underneath equals just scabs.
I hope this helps.