Write an article based on this "Make them wash their hands every time they pick their nose. Occupy their fingers. See a doctor. Ignore it."
In addition to being sanitary, this technique will serve as a nose picking deterrent. If your child is constantly having to stop their play to wash their hands, it will make them think twice about picking their nose. That said, you have to be consistent, even in public. Children will often pick their nose out of boredom. Make sure that they have an activity to do with their hands. Coloring and drawing are always good fall back activities. You can also keep a toy handy for them to fidget with any time they have to sit still. This will keep their hands occupied and away from their nose. There could be an underlying medical cause for your child's nose picking. Take them to their pediatrician to discuss things such as allergies and dehydration. If the pediatrician sees any signs of such issues, they can advise you on how to deal with the problems. Sometimes kids do things just for attention. If the pediatrician is not concerned about the nose picking and nothing seems to work, just ignore it. Over time, most children will lose interest in picking their nose and stop naturally once the attention is removed from it.