[racinghamster]

zak is right, it could be an old battle scar, but does the skin on the wound seem fresh or red? Can you be sure it`s not a recent injury from something inside the cage? It`s probably superficial but a fresh wound can be irritating which causes the hamster to lick and/or scratch at it, so if he`s running about okay, eating/drinking and not looking phased by it, I would say just keep a close eye on it for now. No need to apply anything like saline (salt water) unless the wound is bleeding or you feel it needs it. Robos are the little tank commanders of the hamster species! x