Reset Password using Recovery HD
Boot into Recovery Partition.
Start the computer,then press and hold down command and R keys to start into recovery partition.
When you see the Apple logo, release the keys.
Wait until you see OS X Utilities window shows up.
Move the mouse to the menubar at the top and click "Utilities", then select "Terminal"
from the drop down.
Terminal window will appear.
Type in resetpassword and press enter key on the keyboard.
Do not close the Terminal window
Reset Password Utility window will open with Macintosh HD selected.
Select the user account from the popup menu box.
Enter a new password.
Reenter the new password for the user.
Enter a hint.
Click the "Save" button.
Click in the menubar and select Restart.