When I was 15, I wanted to get my nose pierced too and my Mom wouldn't let me. She told me to write down 10 reasons she should let me do it, and good reasons, not like "cuz it looks cool". So, I did and she let me do it. =) Maybe this will work for you?? I can understand (as a mom myself now) why your mom may think it looks "disgusting", but your own self expression is important. Having your nose pierced or tattoos doesn't make YOU a disgusting person!