First let me say, you need to get your parents consent. To do this inform yourself how the installation works, you need to be able to tell the piercer what they’re doing wrong. It’ll help convince your parents and make the process as safe as possible.
Second I guess it shouldn’t be a problem technically, I don’t think growing is a concern.
You’ll probably have a hard time finding an installer though, even with your parents.
NExT is a good choice if you don’t have locks or anything yet, a magnet in the finger is probably a bit extreme for your age.
Check map.dangerousthings.com for installers.
Maybe check out Lessons learned 📚 and https://youtu.be/m-JH-YO4Lwk and like everything in the wiki category.