I'm still not clear what capacity you're seeing this young person in, but if it's in any of these -- https://www.nysmandatedreporter.org/Man ... rters.aspx
-- I'm afraid that you may be mandated to report here. At the very least, if you have a supervisor or supervising agency, I'd be sure to fill them in on all of this. It seems to me that someone should be filling you in on some of the kind of information we've given you here at work, you know? You should have at least the kind of professional support and information you're finding at a resource like ours. It also may be time to pull someone else into this with you, all things considered.
In terms of talking to this young person about it, it might be helpful to take it outside the real of value judgements -- theirs, yours, anyone else's -- about what is or isn't normal, and talk about things that may be based on those things, but aren't a matter of opinion, like the law. Whatever anyone's opinions may be about a minor sending nudes to an adult, the fact of the matter is that the laws that exist around that are considerable and that engaging in that behaviour carries consequences that could deeply screw up their whole lives and their ability to live them in a way they probably want to. They might not be aware of what it means to live with sex offender status, and that's something someone may need to explain not to "scare them straight" or any of that garbage, but just so they understand the possible outcomes of this behaviour. Not being able to live in certain neighborhoods or work in certain vocations is a big deal.
But again, it also sounds like you're expressing feeling out of your depth in some ways, too, so if you have a supervisor or supervising agency, I would strongly encourage you to fill them all the way in and seek out some extra support no matter what you do. <3