How do i get past this?

Wait a few years

Sorry, but you'll just have to wait until you're of legal age for doing whatever age restricted thing it is you're doing

Lying about your age on TikTok or any platform is a giant no-no if you ask me

And especially given that the only form of authentication is to do a selfie with your ID, good luck trying to use a fake ID on that as I'm sure that they've built in something to be able to distinguish a real ID from a fake one

Get your older sibling or parent to do it