has he been fighting with another dog. my dogs will get marble sized deals under their skin sometimes and i took one to the vet one time who had several. the vet said it was small hematomas and that they would heal up and go away. he said more than likely it was from a dog fight or play. my dogs wrestle and play rough all the time so it sounded good to me. they went away in about two weeks. if it aint that he prolly has a bad case of the ITIS