It looks like fibrous epulis, but it will need to be removed so it doesn't start to give him problems when he eats. The good news is that epulis is always benign and it doesn't spread, but it should be biopsied anyway just to be sure. Please let us know what the vet says.
Ghilly
Gee, never saw something like that but I would definitely have the Vet check it.
Please update and good luck
How old is this dog? Thanks