Patrick Mahomes Regrets Going Ballistic Over Penalty, 'It Was A Foul'

3:38 PM PT -- Patrick Mahomes is sharing his regret over how he reacted in the closing seconds of his loss to the Bills ... admitting after going back and watching the video, it was, in fact, the correct call.

Mahomes did an interview with 610 Sports on Monday ... where he said his actions were unacceptable, especially how he treated Josh Allen after the game.

"Obviously, you don't ever want to react that way," Mahomes said. "I care, man. I love this game, I love my teammates. I want to go out there and put everything on the line to win."

"But obviously, can't do that, can't be that way toward officials or really anybody in life, so I probably regret acting like that. But, more than anything I regretted how I acted toward Josh after the game, because he had nothing to do with it."

Mahomes said he'll learn from the whole thing, as he wants to be a good role model to his young fans ... and he's ready to move on to his next opponent, the New England Patriots.

Patrick Mahomes showed a completely different side of himself after a controversial penalty eventually led to the Chiefs' loss to the Bills on Sunday ... going on a tirade on the sidelines and telling Josh Allen the call was "f***ing terrible."

Trailing 17-20 with just under 1:30 left in the game, Kansas City had a wild 25-yard touchdown play involving Travis Kelce and Kadarius Toney ... but it was called back after officials determined the latter lined up in the neutral zone prior to the snap.

The Bills went on to secure the victory ... and when Mahomes headed to the bench, he had to be held back by his teammates as he unloaded on the referees for what he thought was a BS call -- even throwing his helmet in frustration.

The tensions were just as high when Mahomes met up with Allen after the game ... 'cause instead of simply saying "good game" and trotting to the locker room, the two-time Super Bowl champ continued to rant about the penalty.

"Wildest f***ing call I've ever seen," Mahomes said while embracing Allen. "Offensive offsides in that moment, man ... f***ing terrible."

Of course, the consensus is Toney was visibly offsides prior to the start of the play ... and while Mahomes and Chiefs head coach Andy Reid aren't denying he was lined up in the neutral zone, they felt the sideline official should have either told the receiver to back up, or kept the flag in his pocket.

Mahomes' wife, Brittany, also shared her frustration with the call ... saying the ref was the real "MVP" of the game on her Instagram story.

When speaking with reporters, Mahomes said it was wrong for officials to "take away greatness like that" ... and it was "tough to swallow."

Reid echoed his quarterback ... saying it was an "embarrassing" moment for the league.

As for the refs' side of the controversy, Carl Cheffers said players can check with officials on their alignment prior to the snap ... but ultimately, it's their own responsibility -- especially because Toney's positioning was "beyond a warning."