Might have accidentally change admin user to standard user
Solution 1:
To create a new admin user, you need to reboot into Single User mode once:
- Boot to single user mode (⌘-S while powering on)
- Run
/sbin/fsck -fy - Run
/sbin/mount -uw / - Run
rm /var/db/.AppleSetupDone - Run
reboot
After the reboot, the Setup Assistant should get displayed again (as for a new Mac) and prompt you to create a new user. This user will automatically have admin rights.