I don't really know snakes, but from reading online it might be an injury to the ligaments. Maybe something small like bruising or needing adjustment like this post, maybe worse and needing the vet. Call your vet and ask what to look for. My very inexperienced opinion is if the snake has been like that for days and doesn't eat when they normally would, it needs a vet appointment. If your snake is moving its jaw at all (yawning, adjusting, etc) then that's probably a good sign that it's not serious damage but it still should go in if it's not eating.