A police union honcho went before a Bronx grand jury to testify against a delegate who allegedly fixed a ticket for him, The Post has learned.

Former PBA lawyer Dave Nicholson — a retired NYPD sergeant who now heads the union’s pension fund — was granted full immunity to tell the grand jury how he asked a delegate in The Bronx to take care of the ticket, police sources said.

Nicholson, 45 — appointed to the NYPD in 1985 — was promoted to sergeant three years later, and prior to his retirement in 1994, served as a squad supervisor in the Street Crime Unit. He got his law degree from Fordham, and joined the PBA’s General Counsel’s office in 1999.

Nicholson’s testimony came within the past two weeks, the sources said, adding that several other members of the PBA board have also gone before the grand jury hearing details of a scandal that has rocked the NYPD.

The NYPD’s Internal Affairs investigators are probing up to 500 cops in the ballooning ticket fixing case — and a Bronx grand jury could file criminal charges against 40 or more, sources have told The Post.

Any cop disciplined under the department’s internal system could face penalties ranging from loss of vacation days to termination. But if an investigation finds a cop took money or falsified documents, he or she could be criminally charged with bribery or obstruction of justice.

Precinct cops allegedly helped Bronx prosecutor Jennifer Troiano — who faces a 2010 DWI charge — avoid a drunken-driving arrest after she was pulled over near her courthouse in 2009. Her lawyer denies she was ever pulled over in 2009, and said he expects her to be cleared of the later charge.

DNAinfo.com has reported that cases under scrutiny stretch all across the city, with 380 in The Bronx; 55 in Manhattan; 30 in Queens; 30 in Brooklyn; and seven on Staten Island.

The PBA did not answer a telephoned request for comment last night.

cathy.burke@nypost.com

