Ask the Mom how he behaves when she changes him and ask her advice. Then get out the duct tape tomorrow. JUST KIDDING!!! That's awful! He's almost 3 and usually I have children toilet training by that time and they are getting big enough to understand everything you say to him, so if you tell him he's hurting you and talk to him doesn't he listen? This doesn't sound like a keeper unless the parents can help you out A LOT.