A 21-year-old was shot in the butt on the Lower East Side Thursday morning and hopped a No. 1 train in Inwood before he was found and taken to a hospital, police sources said.

Stephan Matias was discovered wounded on the subway around 7:30 a.m. at Nagle Ave. and Dyckman St in Inwood, the sources said. He was taken to Harlem Hospital in stable condition.

Police determined that the shooting took place hours earlier, around 3:30 a.m., in an apartment at 312 Delancy St. in the Bernard Baruch Houses.

Jontae Kuklu, 17, was arrested at the scene of the shooting in possession of a firearm, the sources said.

The two had been hanging out smoking pot with two other men when a shot was fired, a police source said. It appears that two of the men might have tried to rob the other two, the source said.