Teeth grinding

I'm quite paranoid atm in regards to my rabbits health, he's fine but I did lose my other bunny just over a month ago and then my friends bunny got ill a few days ago so im kinda on the watch out just incase🥲

Anyways earlier, I laid on the floor in front of him and I heard his teeth grinding for like 2secs? Not too sure what that means. I've read it could be pain but he hasn't been hunched over, hes eating n drinking fine, being active. He was loafed up when I heard that noise and he is flopping around alot so could it just be happiness?