Law enforcement sources tell TMZ ... one of the rapper's guards told cops he and Wayne got into a fight at Weezy's Hidden Hills, CA home, and cops say they were told the altercation escalated to physical violence and a brandished firearm.

We're told the guard claims Wayne told him to get outta the house after the initial dispute, but the guard went to the bathroom first and he claims that's when Wayne dramatically escalated things.

We've spoken with a source close to Wayne who strongly denies the incident even happened ... and tell us Wayne doesn't even have a gun.

That's not however, what the guard told cops ... our sources say the guard claimed Lil Wayne pulled out an AR-15 ... and that's when the guard booked it out of the house to the gated community's guard shack, where he called police.

We're told cops went to Weezy's place to get his side of the story, but he was already gone. The guard told police the fight started with Wayne accusing him of taking photos and leaking them to the media.

Other law enforcement sources involved in the case tell TMZ ... cops have issues with the guard's story, and they say he did not have any marks on his body or injuries from the alleged physical confrontation.

We're told the guard also does not want to press charges against Wayne -- and while police have doubts about some of the allegations, they will nevertheless investigate.