The rapper was riding in a car in an all-denim outfit late Tuesday night when she became, uh, uncomfortable -- especially in the crotch area -- because her pants were too tight.

She explained her plight as only Cardi can ... "I hate having p***y wedgies, bro. My p***y be screaming at me like, 'Bitch! You got me f**ked up! You want a yeast infection, bitch?"

So, you gotta watch her remedy the situation by riding bare-ass on the car seat to let her p***y breathe. Cardi can pull this off because ... she's Cardi.

The surgeon general does NOT recommend you try this in the back of an Uber. There could be serious surcharges and/or criminal charges.

This isn't the first time Cardi's been very open and honest in public about her battle with wedgies -- a couple weeks ago at a concert in New Zealand, she stopped the show and told her fans ... "I need a little break. I'm gonna be right back. I gotta take this wedgie out my ass."

The crowd loved it. So does CB's p***y.