You can reset your password using Recovery Drive, or you can start over in a new Keychain. It will also need a password.
Restart and hold down the Command and R keys during start-up to boot into the Recovery Disk Assistant
On top, in the Menu Bar click the Utilities item then select Terminal.
In the Terminal window, type resetpassword and hit Return.
Select your User and type in your new password.
Restart.
Create New Keychain If you do not know the original user password, you should select this option. This will create a new login keychain with the same password as the user account.
Open Keychain Access in Applications/Utilities
Open Preferences under Keychain Access in the Menu bar.
Select General tab.
Click on Reset My Default Keychain