Salt dip or bath would help initially. I suspect that it's a bacteria infection, so lower temps would help with that. You definately want to get him in a QT tank by himself, same water and temp as the main tank. Add salt gradually to 1 teaspoon per gallon, and give him a salt dip twice a day, in a concentration of 3 teaspoons per gallon. You should have him in there for no more than 30 minutes at a time, and return him to his QT tank.
If the spots look better, I'd go ahead and treat with one treatment of anti-bacterial medications, to kill off any bacteria that may be in the water or still on the fish.
In severe cases, I've heard of people tkaing the fish out and applying iodine/neosporin directly on the wound.
Good luck
