tiny broken screw on shield part

hi good morning i was putting back together my iPhone 4 because i had just replaced the speaker housing on it and one of the screws were the shield is one of the tiny screws just broke and its stuck in there i don't want to mess with it before i know what to do i have no idea how to remove it , i don't think this has ever happened to anybody . please if anybody knows anyway of removing it please tell me