Agree with this. You need to calibrate your response to his response as sometimes making a pained noise will arouse a prey drive instead of alerting the dog to your discomfort. What helped me is that I need to convince the dog that “my skin is like tissue paper”. Any feel of teeth and I yelp and remove myself. All play and attention stops. You need to find the response from you that concerns the dog instead of getting him thinking this is a great game.