K.B.
I watch a little boy who does that and his mom started teaching him "Nice" and she would take his hand and gently run it down the side of her face and say "Nice". Now it's funny because he went to go drop a toy very close to one of my daughter's head and she told him "Nice" and he gently ran his hand down his face. It was priceless. But I do understand that it may also be his way of showing affection to you, he gets so excited. I know it can also hurt too, as he's done it to me. Good luck to you and remember consistency. Pick something to say like a one-word phrase and stick to it.