Nose Picking is one of Fallout GURPS disadvantages. See: Fallout GURPS.
You behave, some or all of the time, in a fashion repugnant to others. The worse your behavior, the more bonus points you receive. Specify the behavior when the character is first created, and work the bonus out with the GM. Body odor might be worth -5 points, spitting on the floor would be worth -10 points; -15-point habits are left to the imagination of those depraved enough to want them. For each -5 points your habit is worth, subtract 1 from all reaction rolls made by someone in a position to notice your problem. This reaction penalty is for members of your own race; it is up to the GM to handle differing reactions from other races.”— Steve Jackson Games GURPS sources
With the abandonment of GURPS, Nose Picking was removed from the game