If you are locked out of your computer due to Yubico Login for Windows, an unknown or incorrect username could be the issue. This software doesn't alter your username and/or password to log in, so you'll still enter your username and password to log into the computer. Note that, with most configurations, you should not touch your YubiKey when signing in to Windows with Yubico Login for Windows - doing so with the cursor in either the username or password text field will generate a one time password in the field and result in a failure to log in.
If you have only installed Yubico Login for Windows and rebooted, then the YubiKey is not yet required, although the login screen will look different at this point. Once your system has been rebooted following installation, at the login screen, in addition to your password, you will also be required to enter your username. Most likely, you were only required to enter your password beforehand, as this is the default behavior in Windows. Or you may not have a password set on your local user account, in which case you should leave the password field blank.
Since it is not common to need to enter your username in Windows, you should first verify what it is if you are at all unsure.
Since you aren't able to log in to your computer the "normal way," first start your computer in safe mode (see here for instructions). Assuming you are able to successfully log in after booting in safe mode, open the Command Prompt program from the Start menu, and in the window that appears, type whoami, and press Enter on your keyboard.
The command's output, which should be in the form DESKTOP-1JJKFIDS\jdoe, will contain your username - it will be the portion following the backslash. In this example, the username would be jdoe.
Once you have this, exit safe mode by rebooting, and try again to log in to your computer. If you did not have to enter a password prior to installing Yubico Login for Windows, leave the password field on the login screen blank.
Please give this all a try, and if it doesn't help you can open a support ticket here. Please provide a photo/screenshot of the login screen and a detailed description of what you've attempted so far.