I think there are instances where keeping quiet works, but then there are such cases (as this seems to be) where honesty, being open, and telling it like it is, would work best. There’s a way to inform someone of how you feel regarding their behavior using tact, but also getting your point across. Depending on that person’s personality, they may cop feelings and act like a victim or that the world is up against them, but those will be their feelings and you will have to do what is best for you.
This guy sounds like he needs to be BLOCKED. Period.
And if it were me, I’d have no trouble doing so. I would inform him first, “Hi, yes… I have asked you to refrain from sending me vulgar pics of yourself as I am a mother and my kids have my phone sometimes, and also, I am not interested in seeing anything that I don’t want to see without asking for it first. But since you keep crossing a line that has been drawn, I am blocking you. Be well and take care.”
I hope you’ll do what you feel you must in order to gain some semblance of relief from this person. ❤