A 4-month-old girl was stabbed in the forehead with a pen yesterday afternoon after the woman holding her got into a fight with another woman in The Bronx, cops said.

The brawl began at about 4:55 p.m. in front of a bodega on 165th Street and Union Avenue in Morrisania — and ended when the second woman took out a pen and stabbed the 4-month-old girl in the head, cops said.

A bodega worker said that when he heard the fisticuffs, he ran outside and saw the baby bleeding and the woman who held the baby during the fight running around crying.

The baby was taken to Lincoln Hospital in stable condition and cops are looking for the woman who stabbed her.