We can boot your Mac to a special mode called Single User Mode. Then type some commands/texts there which will force your Mac to bring the new account setup screen. So you can setup a brand new admin account and then use that account to reset the password ***** your original account. This might seem a little difficult, but it is actually easy.
Follow the steps below to create a new User Account in Single User Mode.
• Turn off/shut down your Mac.
• Turn it on and 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 Administrator 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
(If it returns any errors after any command above, then you are entering the commands incorrectly. Make sure you enter it correctly)
When you enter last command and press return, the Mac will shut down. So turn it back on, you should be able to create a brand new Administrator account (when creating the account, if you're asked to transfer information, select Don't transfer)
Login to new account. Then in new account (which will be blank), go to System Preferences > Accounts or Users & Groups, 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.