Am I hurting him?

My nephew is 13 years old. I have seen him picking and eating his own snot, scabs, earwax,and skin from fingers and toes, since he was about 2 years old. I lovingly nicknamed him "Booger" at 2 years old, ad i thought, "he's 2, its funny, and he'Lloyd outgrow it." Last year he finally stopped wetting his bed at night, and urinating and defecating on himself throughout the day. He has lived a hard life with his parents, who are both addicted to methamphetamine. However, he has, for a large part of his life, lived with his grandmother. Grandma spoils him with purchasing any thing he asks for, makes an excuse for ALL of his bad behavior, doesn't let anyone correct or discipline him in her house, and will not speak to anyone who does correct or discipline him for weeks. I don't believe he has ever been to see a doctor about his habits. He has never been diagnosed. When I ask his grandmother about his behavior, she makes an excuse for him or brushes it off. When I "catch" him picking and eating (he tries to hide it), I always ask him his age and then I ask, "why are you still picking and eating that?" He always gets a shamed look on his face and answers, "I don't know." He proceeds to look down and walk away. My question are for the picker: Have you ever been comforted about it? How did it make you feel? Am I hurting my nephew, mentally, by asking him my same old question? How can I help him? Is there something I can say/do to make him feel better about it?