Hello lily_0777111,
Thank you for reaching out to the Microsoft Community and I'll be glad to assist you today.
Based on your description, it seems you have forgotten the username (possibly misspelled when signing in) and the password of the administrator account on your Windows 11 PC.
If you have tried signing in with an incorrect username and also the password matched, it's likely you have accidentally logged into an unknown account and are now locked out.
In this case, it's best to remove the administrator account signed in on the device. To do this, you will need to perform a full system recovery process, which will wipe all data stored on your computer. Afterwards, you will be prompted to set up Windows again from scratch, sign in with the correct account, and enter the correct credentials. This will ensure the account becomes the administrator.
Please note that this process will remove all personal files and applications on the device.
1. On the Windows sign-in screen, press and hold the Shift key while you select Power > Restart.
2. Upon reboot, select Troubleshoot > Reset this PC > Remove Everything and Proceed with Local re-installation.
I hope this information helps. If you have any questions, please let me know and I will be happy to help you further.
Best regards,
Gunasekar N