Sounds like just a little boo-boo. These guys get them easily because of their parchment thin skin. If he's not bleeding or anything, I'd simply put some Neosprorin and maybe a bandaid (to keep him from licking - this dogs will lick...) on it.
BTW: Looks like he had fun at the playgroup! This is familiar territory so often even insecure dogs really come out there. This is a very social breed, and they just shine when with the other dogs.
_________________
Elizabeth
Tiger, aka Ti
Junior, son of Tiger
And All Who Have Come Before