How do I unlock my locked iMac?

After the 1 hour wait try If you forgot your Mac login password and also it would be wise to get yourself a password manager or begin using the Passwords app on your Mac which syncs with your iPhone and/or iPad assuming you own one or both of those. They sync using iCloud and make managing all the logins and passwords you likely have much much more manageable. Use the Passwords app to create, manage, and share passwords and passkeys across Apple devices - Apple Support

Wait an hour, and check the caps-lock key when you enter your password, and try again.

Otherwise, reinstall macOS.

How to reinstall macOS - Apple Support

Restore (migrate) your backup during setup after reloading macOS, if you have a backup. (More generally, backups are the only way to mark data as being valuable. Unfortunately, most of us learn that lesson by losing our data, too.)

Also see: If your Apple Account is locked, not active, or disabled - Apple Support