Choose Tools -> Developer Tools > Error Console, paste the expression: 
  openDialog("chrome://pippki/content/resetpassword.xhtml")  
  and press the Evaluate button. That will open a dialog asking you if you want to reset your password. If Evaluate is not seen, press enter key. When prompted, press the Reset button. 

If you are referring to the Primary Password, here is the solution: Choose Tools -> Developer Tools > Error Console, paste the expression: openDialog("chrome://pippki/content/resetpassword.xhtml") and press the Evaluate button. That will open a dialog asking you if you want to reset your password. If Evaluate is not seen, press enter key. When prompted, press the Reset button. Doing this also removes all account passwords.