Weezy violently coldcocked a bouncer who was trying to do his job- (Lil Wayne)

Lil Wayne violently coldcocked a bouncer who was trying to do his job ... so claims the doorman, who's getting ready to sue the rapper.

The bouncer's attorney -- Arsineh Aghakhani from Los Angeles City Law -- says she's preparing the lawsuit against Lil Wayne for battery after her
client claims the rapper attacked him while working the door last month at Hyde nightclub for a BET Awards after-party.

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We're told Weezy's entourage was upset they got searched, and after an argument erupted ... Wayne allegedly came from behind and punched the bouncer in the face. Wayne's bodyguards also allegedly shoved the staffer up against a wall ... and we're told he suffered a dislocated jaw and shoulder injury. 

As we previously reported -- the bouncer filed a report with LAPD. Wayne has denied punching the guy, but admits there was a brief altercation.