NASCAR's Kyle Busch Apologizes For Using R-Word In Post-Race Interview

More trouble for NASCAR -- Kyle Busch is apologizing for using the r-word in a post-race interview on Sunday ... saying he should have never used the derogatory term.

Busch was furious with Brad Keselowski after making contact with the driver at the NASCAR Cup playoff race at Martinsville ... sounding off to reporters following his 2nd-place finish.

"He drills my ass coming out of (turn) 4 for no reason," Busch said after the race.

"I mean, where was he going? What was he gonna do? Spin me out? He was trying to do a (Kevin) Harvick is what he was trying to do. For what? For second place? To do what, he wasn't gonna transfer through with that."

"It’s frickin’ (r-word), man. So stupid." Busch added. "I don't understand these guys. I should beat the s*** out of him right now, is what I should do. But, that doesn't do me any good, either."

Busch took to Twitter to share his regret over using the term ... saying, "In one of my post-race interviews I used a word I should never use and I want to apologize for it."

It's the third time a high-profile driver has used a derogatory slur recently -- remember, Kyle Larson was suspended after using the n-word during a stream ... and Hailie Deegan underwent sensitivity training after using the r-word.

A spokesperson for NASCAR says the org. is reviewing Busch's comments ... which means sensitivity training, a fine or a suspension could be on the horizon.