a man was arrested for violently robbing his former girlfriend on sept. 24 at 6:15 p.m. at her apartment on west 63rd street near west end avenue. police said that manuel nina, 24, violated his order of protection when he pushed his girlfriend, 18, onto the stairway as she held her young son. he grabbed his girlfriend by the throat and punched her, demanding her ring, which he tried to pull from her finger. nina then pushed his girlfriend into their apartment, cops said. he was arrested on sept. 25 and charged with robbery.