One of the first kids I worked with enjoyed pressure on his face, and I could even use it as a reinforcer that he worked for. He would place my hands on his cheeks/jaw, and I would press them in.
Chewing may be an effective substitute, since it applies some pressure in a similar area. If he does this in a variety of ways, you may be able to just define a set of appropriate "chinning" locations/techniques and inappropriate ones. For example, the arm of the couch may be ok, whereas other people's bodies would not. Or you could even be more specific - dad's shoulder is ok, mom's is not, etc. Then you can just redirect him to the appropriate ones when he starts doing it. As long as you're consistent about which types are ok, and which are not, he should be able to learn the distinctions and be able to contain it to those. One thing to consider (if you say it's ok to do it on your shoulder) is how it will play out if he keeps doing this for the next 10 years. So pick things that will still be effective / appropriate for a much older child / teen. That way you won't have to change the rules on him.