Hello, Cece E
Welcome to the Microsoft community.
Thank you for your feedback. Based on your description, it looks like you need to verify your administrator account to log in. I have tested your issue and if you are unable to log in by verifying your administrator account, you can only try to reinstall windows using the USB installation media.
How to: Perform a Custom Installation of Windows 11 and Windows 10 - Microsoft Community
For file backup, you can refer to the following link:
Rescue Files when Windows Won't Start - Microsoft Community
I look forward to your feedback.
Best Regards,
Aaron| Microsoft Community Support Specialist