NBA YoungBoy will be cooling off in jail for a while longer after his arrest for allegedly assaulting his girlfriend -- the judge just ordered him held without bail.
The 18-year-old rapper's been transferred to Georgia's Ware County Jail -- where he got a new mug shot -- and faced the judge. TMZ broke the story ... YoungBoy was busted Saturday night in Tallahassee on a kidnapping warrant, related to the attack on his gf, Jania.
Cops say hotel surveillance video shows him body slamming her and then dragging her -- allegedly against her will -- back into the room. Jania has said they were just playing around, but the judge obviously ain't buying that.
He's currently facing felony kidnapping and aggravated assault charges.