Nick Carter attacked and choked an employee in the Key West bar where Nick got arrested ... according to the lawsuit that the employee just filed.
Skylar Carden is the bouncer, and in the lawsuit he says the Backstreet Boy was originally escorted out of the Hog's Breath Saloon for his "unruly and disrespectful" behavior. He says that's when Carter got physically aggressive -- "striking and choking" Carden.
Sources connected to the bar described the alleged assault as Carter squeezing Carden's larynx.
We broke the story ... Carter was busted for misdemeanor battery. Nick has said, "the truth will come out."
Carden's attorney, Mark DiCowden, says Carter is nothing more than a "backstreet thug" who inflicted mental anguish, pain and suffering on Carden. He adds his client was just doing his job and didn't deserve the attack.