The 32-year-old, who has made 20 appearances this season, suffered the injury during the goalless draw with Gillingham on Tuesday night.
The former Exeter defender wrote on his Twitter account: "Fractured my fib 4-6 weeks I think should know more next couple of days!"
A club spokesman confirmed that Challinor will need to wear a pot to help the injury heal, while Gary Mills told the York Press it was "a big blow" for the Minstermen.







