Rob Gronkowski -- YES, I'VE BEEN CHEATING ... On My Diet, Bitches!

To the victor, GO THE CHEESEBURGERS ... so says Rob Gronkowski who tells TMZ Sports he's been on a celebratory cheeseburger binge ever since he won the big game.

"I've been eating cheeseburgers off the charts," Gronk told us out in NYC earlier today.

Don't worry, the burgerfest is only temporary ... Gronk says he'll be back on his regular diet in just a few days -- but if anyone's EARNED a burger break, it's this guy.

Bonus -- Gronk told us he'll be spending time in L.A. this summer and says he hopes he can continue making waves in Hollywood ... where he's already landed a movie role ("Entourage") and TV cameos ("Whose Line Is It Anyway?").