Nature probably intended for people to pick their noses. It is very likely that people have been picking their noses since before there were even people. In other words, there can be little doubt that our prehistoric ancestors were nose-pickers and so it's interesting that picking one's nose is something that just isn't done in front of other people, at least not intentionally except perhaps as part of some sort of rude joke. Unsurprisingly, there are lots jokes about nose-picking. (A favorite of mine is the one about the snowman looking through a bag of carrots. He was picking his nose! LOL) This video exploits the phrase "digging for gold" as it relates to the habit of cleaning out the nostils with one's fingers. In fact, sometimes if one observes a friend picking his or her nose, one might joke about it by asking them if they picked a winner or if they hit the mother lode. Of course, depending on the popularity or social status of another child caught picking his or her nose, children will sometimes ridicule a child caught in the act. Various sources indicate that most people admit that their favorite place to pick their nose is in the shower!

BTW, rhinotillexomania is a term used to refer to compulsive nose-picking.