TMZ Sports talked to Gang Green legend Nick Mangold after the Jets blew a 16-point, 2nd-half lead at home ... and the former All-Pro who played 11 seasons for the team says he's hurtin' after the L ... but there's a lot of football to be played.

"That stung. Being up 16 to nothing with, I think, like 2 minutes left to go in the 3rd quarter, and to see it crumble away with the missed kicks, not really finding a rhythm on offense, not capitalizing on those 4 turnovers, that hurts. And, so it's gonna be a long road 'til Monday when we can play again."

"Hopefully, the guys are gonna get back in the building, they're gonna put their head down, they're gonna get to work, and that's all you can ask for."

But, how 'bout franchise QB Sam Darnold -- who threw for 175 yards and a touchdown -- but wasn't exactly moving the ball up and down the field???

"I think Sam was doing as well as he could. The offensive line, having not played in the preseason together, and still working out some of the kinks and everything, you kinda expect some hiccups here and there."

"You gotta give credit to the Bills defense too. They were flying around making plays. I think with another week of practice, another week of being together, hopefully we'll shore things up as we get ready for the Browns."

Bottom line ... nobody panic.

"We'll keep grinding. It's still a long season. 15 more games to go. If they win all 15, you'll forget about this one completely."

We also talked CBD with Nick (he's working with a company called MotiveCBD -- who specialize in products for athletes) and Mangold tells us what Cannabidiol has done for his body after 11 seasons of pro football.