A perv sexually assaulted a woman on a Manhattan train — and then shoved her when she took his picture, cops said. 

The 23-year-old victim was riding a southbound 1 train approaching the 28th Street station in Chelsea around 11:25 a.m. Monday when the man stood next to her and placed his exposed penis on her right arm, authorities said. 

Both the victim and suspect got off the train at 28th Street, where the victim confronted him and started snapping photos of him, cops said. 

The suspect then allegedly swiped the victim’s phone from her hand and threw it to the ground, damaging it. 

He shoved her and then ran off, cops said. 

The victim did not report any physical injuries. 

Cops released two images of the suspect, one taken from the victim and the other from a surveillance camera. 

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