An on-duty NYPD officer suffered injuries Thursday after chomping on a razor blade stuffed inside a steak sandwich he’d just bought from a Queens deli, sources told The Post. The nasty surprise was tucked inside the hero he’d purchased around 4:30 p.m. from Bon Appetit Specialty Food Store on Beach 129th Street in Belle Harbor. The 24-year veteran, who was in plainclothes at the time and assigned to the critical response command in the counter-terrorism bureau, suffered a small cut in his mouth and was treated at Nassau University Medical Center. The NYPD is investigating how the razor blade ended...