Well actually it depends on whether or not he chewed it up, which if so he would most likely be fine, or if he swallowed it whole, in which case it could cause a problem with impaction. It won't digest or get smaller if it was swallowed whole so you will need to watch his poop for it and if he shows any distress have him seen by the vet. If he chewed it up then it should pass, as Karen said.