Unlocking Systems Preference with Administrator Password

at minimum do an SMC reset and a Pram zap.

How to reset the System Management Controller (SMC) on your Mac - Apple Support

Reset NVRAM or PRAM on your Mac - Apple Support

Reset the NVRAM and SMC, as you've been told already, is the first thing to try.

Did you try changing your username recently? This is known to turn what used to be admin users into standard users - and that, of course, is a problem if there is only one account. There is a procedure to solve that, but maybe this is not your situation?

There is a solution - assuming you do not have set a firmware password, and do not have FileVault active.

If that is your case, follow the instructions below.

When your mac reboots after doing these instructions it will act as if starting for the first time; choose not to import anything and follow the indications to create a new user account (which will automatically be an administrator). You will then be able to use this new account to clear the password for your regular account and be back in business.

Start in Single User Mode by holding Command-S at startup.

Then you need to type following commands at the prompt:

/sbin/mount -uw /

rm /var/db/.appleSetupDone

reboot