Chris Brown Head Stomps Fan at Concert

4:00 PM PT -- Mokrani doesn't know what the hell Chris is talking about ... he tells us he was NOT working security at the club.

8:55 AM PT - Chris Brown posted on social media and said Mokrani was a security guard who assaulted him and tried to kick him out, so his team "handled the situation accordingly."

Chris Brown exploded in anger and stomped on a man's head during a concert ... and the victim is now gunning for some justice.

Malek Mokrani attended a Brown concert in Cannes on May 18 ... it's clear a fight erupted and something clearly upset Chris, because you see his shoe turn into a weapon.

It's unclear if Mokrani was involved in the fight or just collateral damage.

He tells us he went to the hospital with neck and head pain and plans on filing a police report.

We reached out to Brown's rep. So far no word back.