A man stabbed a woman in the head with a pen on the subway during morning rush hour Tuesday after she complained that he lit a cigarette inside the car.

The incident happened at about 9:15 a.m. on the downtown 3 express train as it pulled into the Chambers Street station, according to police.

The man and the woman had gotten into an argument over the lit cigarette when the man pulled out a pen and stabbed her in the head, police said.

Passengers ran to alert the conductor after the train pulled into the station.

The woman was taken to the hospital, where she was treated for a minor flesh wound, said police.

The attacker, whose name was not immediately released, was arrested and charged with assault.