My mother in law's finger always seems to be in her nose, I'm always having her wash her hands. I will not eat anything she touches. She loves to taste food when I'm cooking, I will not have it. She gets livid when I tell her to please stop picking her nose. She's so stubborn, I gave up telling her to change her pull up so I just left it up to her, she changes 2xs a day.
When I ask my mother why she does it she says it is because her nose feel crusty. I personally think it's more about boredom. I sure hope I don't turn into a nose picker down the road. Alas it may be heavy in my genes.