It's a phase, and probably nothing more than that. As long as he doesn't seem to be in pain or ill, then I would keep doing what you're doing! By distracting him, but not making a big deal out of it, you'll help him find other more interesting things to do. :)
My son used to stick objects, like toys, too far into his mouth until he gagged. Totally freaked me out, and I overreacted! Then I had to UNDO the damage I had caused, because he did it over and over to get my attention after that! (Before that, I really think it was just some weird new thing to do...) So I took the toy away gently and distracted him each time. After a little while, he stopped on his own. Ignoring isn't always as effective as gentle redirection.
Your kiddo is very close to being a toddler. And toddlers are weird! They do the strangest things...and all you can do is go along for the ride, and try to figure out what's dangerous vs. what's just quirky...
But talk to a doc about anything you're really worried about. If it really feels like something is wrong, then call!