A Metropolitan Transit Agency worker was punched in the face after stepping in to break up a subway argument Thursday — just steps from where a sword-wielding wacko murdered an innocent man this week.
MTA track worker Michael Grosso, 59, was on duty a little after midnight, working on the southbound A/C line in the Jay Street station, when he spotted a man arguing with a passenger on the platform and decided to step in, police sources told The Post.
However, Grosso quickly became the next target…