You can give him ambesol for topical relief... just dab some on with a q-tip or cotton ball, just as you would do for a child.
You can give him Bufferin in 10-25 mg (per every 2 lbs of the animal) up to twice a day for pain.
You can also give liquid tylenol but you'd need to call your vet first for dosages.
Also you may want to try getting one of those baby teething rings that you freeze (they make them for dogs as well) and see if that helps him out. OR wet an old sock, put it in a sealed baggie and freeze that for him to chew on.