Your dog is gorgeous btw..
But anyway, my dog had this the other day, because my other dog chewed his ears while playing outside. I took him to the vet and he said it was probably a really small frost bite and the fact that the other dog chewed on it, it made it worse..
He didnt gave me any medication to put on, or anything, so I don't think it's nescesary to bring yours to the vet. Anyway, if it gets worse, vet ASAP. But for now, just keep an eye on it