James Griffin, 41, was in good condition at Bellevue Hospital Thursday night, according to police.
The 18-year NYPD veteran, assigned to the emergency service unit, had a concussion, and suffered a gash on his forehead and a broken right wrist, police said.
"He actually apologized for me having to go to the hospital," said Lt. Michael Licitra, who responded with Griffin to the report of man on the tracks.
Two other officers were chasing the man on the road bed of the southbound N train shortly after 7 a.m., when Griffin and Licitra tried to cut him off, according to Licitra.
"In the struggle, James fell down and hit his head on the rail," he said. "He was holding his head. . . . I was still wrestling with the gentleman on the tracks, so I couldn't immediately direct my attention to . . . [Griffin] until we had that person in custody."
In the ambulance, Griffin regained consciousness. About an hour later, he was joking, the lieutenant said.
"He's a great guy . . . trying to make light of the situation," Licitra said.
The encounter disrupted N and R train service for about 18 minutes, police said.
Richard Wilcox, 29, who police said is homeless, was charged with two counts of reckless endangerment, obstructing governmental administration, resisting arrest and criminal trespass.
Griffin is expected to leave the hospital Friday.