Wear a mouth guard if you're worried about your teeth. Not the regular sports one, go to a place that sells boxing and martial arts stuff and get a combatives double mouthguard. You don't need the massively high end one, you aren't gonna stopping a freight train with it; just get a small lightweight one that'll be comfortable and that has a good breathing opening.
Otherwise a hit to the skin will most likely make you bleed, but it won't leave a mark much bigger than the actual BB.
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