Mohsni sparked a pitch battle at the end of this month's Scottish Premiership play-off final second leg at Fir Park when he kicked and punched Erwin after the Motherwell player tried to shake his hand.
The France-born 27-year-old was sent off after the final whistle of Rangers' 6-1 aggregate defeat, which condemned them to another season outside the top-flight.
He was then hit with a four-match ban, extended to seven matches after Scottish Football Association disciplinary bosses found him guilty of two further offences during a Hampden hearing.