"It sounds ridiculous that a broken finger can keep you out of action for a month but that's doctor's orders," Stewart told the club's official website.
"I'm going to have a splint in place after the operation and wires coming out of the top of the finger so I can't play for fear of injuring an opponent.
"It's agony for me to miss out. I want to play for the club I love but for the next few weeks I will be restricted to watching from the sidelines."