Restart the Mac hard (usually: hold the power button for ~10 seconds), and see if it figures out you've changed your Apple ID password.
If the Apple ID reset sequence then still fails, then you're here: If you can't reset your Mac login password
There's a less-than-supported path involving the .AppleSetupDone file:
https://apple.stackexchange.com/questions/321546/ive-lost-administrator-access-and-var-db-applesetupdone-is-read-only
...but if you do follow that path, I'd get a backup or two and then wipe and reload from the backup.
With a forgotten or otherwise unavailable password, your keychain will also be inaccessible.