An Ohio man claims Justin Bieber confronted him inside a bar and SPIT IN HIS FACE this weekend ... all because JB thought he was secretly taking pics.

The man -- a DJ who performed at the Social Room on Park Street in Columbus, OH earlier that evening -- called in to the Dave and Jimmy show on WNCI and explained the saga ... saying it all started in the VIP room.

"Two of Bieber's bouncers approached me and said I was trying to take pictures of Bieber."

The man thinks JB was concerned because it was a 21+ night in the club ... and Justin's only 19.

The DJ says Bieber's people grabbed his phone and started going through it looking for pics -- but didn't find any. Still, the man claims, the bouncers told JB the DJ was trying to take pics.

According to the DJ, Justin approached him moments later ... and spouted off a couple of "choice words."

"He called my mom something, called my dad something, called me something ... and spit in my face."

TMZ spoke to the DJ ... who tells us he plans on filing charges. He's also been tested for hepatitis ... but says the tests came back negative.

The DJ's story is interesting because it's not the first time Bieber has been accused of spitting in someone's face. The singer's neighbor in Calabasas made the same allegation when he confronted Justin about speeding in their gated community.