A demonstrator chucked a beer bottle at a police officer during a protest outside the nail salon where a “racially charged” melee took place, cops said Tuesday.

The protester was in a crowd of about 50 people when he launched a bottle that struck a detective in the head at Martense Street and Nostrand Avenue at about 2:30 p.m. on Monday, according to police.

The crowd was protesting the Big Apple Nail Salon where a fight erupted days earlier when a botched eyebrow job turned into a heated altercation. The customers claim the incident was racially motivated.

The detective who was hit with the bottle was transported to an area hospital where he was treated and released.

Cops were looking for the bottle thrower on Tuesday night.