No, it's not associated with pedophiles and whoever told you that is wrong/misinformed/confused.

The symbol you're referring to is called a valknut, and is an old Norse/Germanic symbol most often found on graves alongside images of the god Odin, and appears to have been a symbol of death, likely death in battle. In its correct modern context, a valknut is a sign of devotion to the god Odin specifically in his role as a psychopomp, but you should NOT wear it as a tattoo. (That basically says "I'm ready to die. Kill me now.")

Unfortunately, this symbol has been so heavily coopted by white supremacists that it can no longer be used in its correct context, although it's sometimes used by queer heathens in Pride flag colors as a way of saying "up yours" to the white supremacists (who are, of course, also very often homophobes).

In this context, it's white supremacist BS, and I doubt this guy knows what it means even at the more basic level of "I am willing to die in battle for my cause."

The tree below it is a World Tree/Tree of life, btw, which is a symbol he has even LESS business wearing.

He's not mentally ill, he's a plastic shaman using symbols he doesn't understand in his search for ill thought out enlightenment as well as an obvious white supremacist. But probably not a pedophile, and that's certainly not what a valknut means.