Help! I accidentally restored Macintosh HD to OS X Base System. Didn't know that would

Help! I accidentally restored Macintosh HD to OS X Base System. Didn't know that would cause issues... I can only open my laptop through the Command+R thing with macOS Installer.

I was just trying to delete everything and start my Macbook fresh. I tried to re-install OS X Sierra, and it keeps failing. When I go to disk utility under internal, there's no Macintosh HD there's only OS X Base System.

Tried to ask Apple Support for help and they first told me to try first aid and that failed.