My MacBook can’t load into macOS?!

Hello Apple Community,

the MacBook here is a 2019 MacBook Pro with Touch Bar and Touch ID. Today, I was trying to add Apple Pay onto my computer when it asks me to turn on “Full Security.” I remember turning it off when I installed Bootcamp on it a while ago, but uninstalled it.

I followed the guide on Apple’s support website, but when I pressed Full Security when in Recovery Mode, it asked me to set a startup disk. So I clicked Macintosh HD, it doesn’t work. I didn’t want to click the other one, so I restarted my computer.

To my surprise, I can’t load back up to macOS. Is my computer done for? Please help me out.