more than likely he'll be just fine. Look in the poop (great fun I know) and you'll probably see part of the bone in a day or so. I"d just look for changes, is he acting funny, tired, uneasy, trouble going to the bathroom, blood in the stool, although even if there was any bleeding it would be higher up in the GI and you won't see red blood anyway, if his abdomen gets sensitive, lots of vomiting things like that.
Otherwise just wait a few days, you probably won't notice anything and all will be well.