Former Gambino crime family boss John “Junior” Gotti walked into a Long Island hospital clutching his bleeding gut Sunday night and calmly asked stunned staffers for a doctor, officials said.

Syosset Hospital employees called Nassau County cops at 9:45 p.m. after the former mob star claimed he got stabbed in the stomach after breaking up a fight between strangers in the parking lot of a CVS pharmacy, DA sources said.

But the son of late “Dapper Don” John Gotti quickly clammed up when Nassau County cops interviewed him at the hospital and became politely “uncooperative” sources said.

“He didn’t say anything to us so there was really no lead to track down at that point,” a police source said.

Authorities are privately suspicious of the Good Samaritan story, sources said.

The Nassau district attorney is investigating the stabbing and plans to speak to CVS employees and to check for any surveillance footage of the purported melee.

A source said that Gotti is under no obligation to cough up information about the details of the incident but that a prosecution can still be pursued without his assistance.

Gotti’s injuries were not life-threatening and he was released Monday, sources said.

His attorney, Charles Carnesi, said he hasn’t spoke to his client about the incident after leaving him a message Monday.

“I expect him to return my call at some point,” he told The Post. “I don’t know what happened because I haven’t spoken to him.”

Touting his departure from La Cosa Nostra, Gotti claims to make his money legally these days with a series of real estate ventures and other above-board business interests.

The hulking Queens-bred mafia scion was the target of four federal trials between 2004 and 2009 — all of which ended in mistrials. Federal prosecutors said they would no longer seek cases against him.

Gotti had been in talks to assist in the production of a movie about his and his dad’s life.

The mellowed mobster lives at his gated Oyster Bay estate along with his wife, Kimberly, and their six children.

No one answered the door at the residence Monday night.