J.M.
i have found that when it comes to the things that little boys will do, its never silly to ask for advise. both of my boys used to yank on themselves.( my 3 1/2 still does) i would get so imbarissed if he did it in public. there father used to say thats what all boys do, but moms are different. i used to tell them if you pull on it it will fall off. now my oldest would laugh and then stop, but my youngest now he just laughs and continues on. i think this is something all boys go through and its part of exploring themselves, (like with the nose)if you just tell them its not nice to do, and leave at that eventually the polking and other forms of investigating will stop. good luck and as i have found sometimes humor is the best medicine.