Police were searching on Thursday for a suspect who followed a 45-year-old man into a Brooklyn subway station and slashed his cheek after the two got into an argument about blocking the turnstiles, a police source said.

The argument started at about 6:30 p.m. on Sunday, when the victim told the man he was blocking the turnstiles at the Essex Street station and to move because people couldn’t get through, the source said. But the suspect, described in his late teens or early 20s, allegedly said he wasn’t moving and instead grabbed the victim’s LG phone and threw it.

The suspect then followed the victim onto a southbound M train all the way to the Myrtle Avenue station, police said.

When the men got off the train, the suspect pulled out a box cutter and slashed the man’s left cheek.

The victim was then taken to an area hospital in stable condition, police said.