'Maybe you lose finger.'

I used to teach both children and adults at my former job. I got along quite well with most of the adult students. Over time we got to know each other fairly well. One day a woman student of mine informed me of the fact that if a young woman in Japan has tattoos there is the possibility that she may have yakuza associations of some sort. I was advised not to get too intimate with this woman until I was sure of her standing that way. My student's exact words were, "If you rub her, maybe you lose finger." Got it, thanks.