There’s a hidden password reset utility in macOS Recovery that will allow you to change the password of any user. Given that FileVault is disabled, no authentication is required to use this utility.
Restart your Mac while holding Command-R. Release when the Apple logo and a progress bar appear. When the Utilities menu appears, go to the very top of the screen and click on Utilities, then choose Terminal. Execute this command:
resetpassword
The Password Reset Assistant should appear. If all goes well, you should be able to select your user account and change your password.
Hope this helps!