If you want a piercing (anywhere) and your parents object, there's not a whole lot they can do if you are an adult. Go and do!
I wanted to get my ears pierced when I was 12. As I was a child, I needed a parent's permission. My father was dead set against it because it was "barbaric" (and we're talking
ears here
) - but I gave such a convincing argument to my mother that not only did she sign for me, she signed up to get her own ears pierced!
Their only stipulation was that I go to a plastic surgeon (which is expensive but arguably safer). It was my personal choice not to get any additional piercings.
You must be very careful. Go to someone who knows what they're doing. Keep in mind that you may have to keep to gold rather than surgical steel. And remember what may happen if you become pregnant.