Anything you put on it, he will lick off. If possible to give penicilin for 3 days, sub-cu, that would be my choice. If not possible, just keep a close eye on it. He will probably keep it clean. The key to a puncture is that it doesn't scab over and become an abcess. If the animal is able to reach it and lick it, they prevent a scab from forming, the wound can drain, and it will usually be ok on its own.