We can create a brand new administrator account, then reset the password ***** your current account from that account.
Follow the steps below to create a new User Account in Single User Mode.
• Reboot your Mac
• Immediately hold down the Command(Apple) and S keys together for 10 seconds to boot into Single User Mode
• When you see the text prompt, type in the following terminal commands to create a brand new Admininstrator account (hitting return after each line). Also, note down the spaces between the commands, like a space between mount and -, space between -uw and / etc
mount -uw /
shutdown -h now
After rebooting, you should be able to create a brand new Administrator account. Then goto System Preferences > Accounts, select your old account and change/reset the password. Then logout from Apple menu and login to the old account.
If you get any message about keychain, then follow the steps below to solve it.
Open Keychain Access, which is in the Utilities folder within the Applications folder.
From the Keychain Access menu, choose Preferences.
Click General, then click Reset My Default Keychain.
Authenticate with your account login password (the password ***** reset earlier).
Quit Keychain Access.
If you have any difficulty on following the steps above, please let me know and I will walk you through it.