Some possible options:
A.
Create a New User Account if You Cannot Access Your Admin Account
Reboot the computer. At the chime press and hold down the Command-S keys to start into Single-user Mode. You will boot to a black screen with scrolling white text, release the keys and wait for it finish.
Enter the following lines at the command prompt pressing RETURN after each:
mount -uw /
rm /var/db/.applesetupdone
reboot
After you reboot the computer you will be taken to the Setup Assistant. When you get to the point where you are asked to setup your new user account, create a new admin account. Be sure to name this user account something different than the admin user account that already exists on the system. When you finish the Setup Assistant, it will automatically log you into the new account.
You can transfer your files from the old account to the new one. See: Transferring files from one User Account to another. Once you have moved all your files into your new account, you can delete the old account using Accounts or Users & Groups preferences.
B. From Standard to Administrator - Hack Mac
C. Mac OS X 10.6- If you forget your administrator password
D.
Restore Admin Status to User Account - Snow Leopard
Boot from the Snow Leopard DVD to enable the root user:
After the installer loads select your language then click on the Continue button. When the menubar appears choose Reset Password from the Utilities menu. Select the account to reset password, choose System Administrator (root). Enter a password and verify it. Save the password, then exit the installer and restart.
Perform change to Admin Status:
At the login window, or if you have it set to auto-login then log out to return to the login window, choose Other... and enter root (all lowercase) as the name, then the password that you set. As root you will have full access to the system including granting admin rights to the accounts that are standard at the moment. You also will see some additional folders on the hard drive you couldn't see before. Do not touch these in any way or you could hurt the OS. Access System Preferences->Accounts, select one of the non-admin accounts and check the box next to "Allow user to administer this computer," then log out and into the account to which you just gave admin status.
Disable Root user:
To disable root go into Accounts preferences from the admin account, click Login Options at the bottom of the list of accounts. Click the Join button next to the words Network Account Server..., click Open Directory Utility, click on the lock icon and authenticate to make changes. Under the Edit menu, choose Disable Root user.
Consult this Apple support article if you get lost.