An off-duty New Jersey state trooper accidentally shot himself inside Penn Station while tinkering with his holster, authorities said.

The trooper, who was not publicly identified, inadvertently discharged his weapon at about 9 p.m. Sunday while standing on a train platform at the transportation hub, the New Jersey State Police confirmed to The Post.

The trooper, who shot himself once in the leg, was wounded while “adjusting his holster” on the platform, NJ State Police Lt. Jeff Flynn said. He was taken to Bellevue Hospital, where he was treated and released. No other injuries were reported.

The unnamed trooper joined the department in September, along with 164 other recruits. An investigation into his actions is being conducted “internally,” Flynn said.

NJ.com reported that the shooting occurred on a platform in the area of an Amtrak train, but State Police Sgt. Lawrence Peele said he did not have more specific information.

“I do not have information on his travel itinerary,” Peele wrote in an email in reference to the off-duty trooper.

NYPD officials referred inquiries to Amtrak authorities and MTA Police. An MTA spokesman said Amtrak officials responded to the incident, but had no additional information to provide.

A spokesman for Amtrak, meanwhile, referred additional questions back to the NJ State Police.