Sgt. Michael Miller, 38, and his partner, officer William Reddin, 30, had pulled over a speeding cab Friday night and asked two apparently nervous men in the back to get out.
One man took off and the other resisted when the officers began to handcuff him after detecting the gun, The New York Times reported Monday.
At one point, Miller said, both he and the man had a hand on the .38-caliber revolver. The sergeant wrested the gun away just as two back-up officers arrived.
"At that point I was completely winded, gassed," he said. "I had a little bit of shock. And it sunk in then what happened. I realized that my ring finger around the nail bed had been wedged between the hammer and the cylinder of the gun and basically getting crushed in there.
"During the course of the fight at one point I felt the gun right up against my belly."
The suspect, Eugene Graves, 30, of New York was charged with attempted murder of a police officer, weapon possession and possession of a controlled substance. The man who ran off was still at large.
The cab driver was not charged, the Times said.