A Manhattan man was slashed in the back of his head during a fight that started inside the Lower East Side bar Karma, police said Tuesday.

The large brawl broke out inside Karma Bar and Lounge on First Avenue around 3:30 a.m. Sunday and spilled onto the sidewalk.

That’s when the man pulled out a sharp object and slashed his 25-year-old victim, causing a cut to the back of his head, cops said.

Police said the men did not know each other.

The victim was taken to Lenox Hill Hospital and needed stitches. Cops are still looking for his attacker.