Should i tell his parents?

Me and my neighbors 17 year old son work on my drag car often and one day he was showin me pics of a brand new Mv engine and he mistakingly went by a pic of a naked girl (me being a man) I asked him who was that? And he replied back "my niece" and it just got awkward from their I just left it alone and he knew I thought it was really weird. After about a minute of silence he says "where really close" the girl was fully naked in the pic she couldn't have been any older than 14-16 I judge the age based on his only sisters age which she is 31. She I tell his mom?? I don't want to look like the perve here. This happen a few hours ago