The maggots have probably actually prevented infection by eating the dead and diseased tissue, but yes, put something on the wound. I suggest Vetericyn and an anti-biotic ointment. If you want to keep him with the flock, paint the wound first with Blue-kote, let dry, then put the Vetericyn on, then lastly, the ointment.
You want to keep the wound moist. The ointment will help with this. It's almost impossible for a wound to grow new tissue if it is allowed to dry out. It also encourages infection, so clean the wound every day, and re-apply the three wound care products.