Can I buy a nose stud from a local store if I'm 12yrs?

I'm 12yrs old and am going to pierce my own nose as my parents will not take me to get it done proffesionally.

I need to know, can I be sold a nose stud at the age of 12yrs? Will they ask to see if my nose is pierced or why I need it or will they ask for my parents permission first?