I need some Advice

try putting something bitter, sour or that he would just find disgusting on his nails, as for the booger problem just keep re-inforcing to him that it is gross.

This sounds mean but it was what my granny taught me to do with my kids, and it worked. put alittle spicey something on his fingers and let them know if the fingers go digging then nosey will burn.And if the fingers are in the mouth I'll hurt.Also vinegar,wash his hands or fingers in it, it smell bad and tastes gross to kids.

kids well be kids lol....my sister had an awful habit of biting her nails as well my mom got fed up with it and dipped one her fingers in Texas Pete hot sauce and it really helped she completely stopped bitting her nails altogether but to this day anything hot she'll eat it lol

Hi! I advised this to one of my students before, who kept on biting her fingernails. Since your son takes to biting his nails and eating his booger through his fingers, too, I advise you to paint his fingernails with colored nail polish. Do it also on his toenails because he tends to bite those, too. Tell him that nail polish is toxic if ingested or taken in (don't worry, there are non-toxic nail polish if ever you're afraid for his health). Since the polish is colored, he would easily see those and be reminded. My student was successful at breaking the habit with this advice. Hope I was able to help you somehow.