Piercing vs. Parents

I'm almost 18. I'm graduating earlier in earlier than my other classmates. I have been chosen to apply for a scholarship with 3 choices of what colleges I want to go to. I want to reward myself by getting my belly button pierced. I have been wanting one since I was 16 but I wanted to wait until I was 17 or 18.

I make my own money, I have my own bank account, I pay for my phone bill, and I pay for certain things I need. I asked my parents if I could get one since I have been making good grades and being able to graduate earlier than my other classmates. They laughed and they said no and that I'll look like a hoe.

So I'm just kinda upset about this to be honest cause I rarely get to reward myself for something this big. I have been saving up my money to go see my boyfriend on his Bootcamp graduation day. I don't mind taking $20 - $45 to get it pierced cause I already bought the piercing a year ago. I just need their consent to do it that's the problem.