Justin Bieber -- Nightclub Spitting Accuser Files Police Report

The DJ who claims Justin Bieber spat in his face inside of a nightclub in Ohio last week has lawyered up -- and filed a police report against the singer ... TMZ has learned.

The man behind the allegation is Addison Ulhaq -- a DJ at the Social Room in Columbus -- who told police the trouble began on July 13 when Bieber's security team thought he was taking pictures of the singer inside the VIP room of the club.

Addison -- who's a junior at Ohio State University and a neuroscience major -- says he didn't snap ANY photos ... but Bieber didn't buy his denial and cussed him out and spat in his face.

The police report, obtained by TMZ, reads -- "The victim stated that the suspect told him that 'His mother was a bitch, his father was a bitch and he is a bitch.'"

Addison's lawyers say Bieber's spit assault left saliva and mucus in Addison's eye, nose, and mouth ... disgusting.

Following the alleged altercation, Addison said he got tested for Hepatitis, but the test came back negative.

In the police report, cops note -- "The victim stated that he does not want anything done at this time and just wants to document the incident."

It's unclear if Addison plans to file a lawsuit ... but it definitely looks like he will.

So far, no criminal charges have been filed.