When my daughter would skin her kneee or something that was obvious and visible, I would take her hand, place it on the boo-boo and say, "Ouch, knee" and give her some type of reinforcement for iitating it. eventually, took years she has somewhat genralized the concept, if I ask her "tocuh boo-boo" or "touch ouch" she will touch her throat or mouth or tummy or whatever hurts at that moment.

There is an app that lets kids who are non-verbal tap what's wrong. Check it out on iTunes apps if you have a smart phone or apple product

Thanks everyone! all great advice. Tucker works with a speech therapist, OT, PT and ABA.... hopefully PECS will work!

Good answer also. My friends daughter is non-verbal but she got her a communication device it has pictures on it like the cards and can work it very well!

Picture cards.