to pick your nose = put your finger inside your nose to remove dried mucus [ˈmjuːkəs] (a thick liquid that is produced in parts of the body, such as the nose)

boogers (informal) = the things in your nose that you pick out

earwax = the yellow substance produced inside the ear to protect it

gross (informal) = very unpleasant to look at or think about [= disgusting]