putting modified mysql password in config.php

Hi 

I am very new to moodle  and using 2.6 . My moodle was working fine but I changed password of mysql user through phpmyadmin . I forgot that moodle also is using same userid to connect to DB. So ofcourse after the password change moodle is not workign as it cant connect to DB 

Unfortunately I dont know previous password so I cant go back to old password and not sure how do I modify config.php to reflect the new password as it seem to be keeping password in encrypted form 

Sure someone must have faced similar issue and will appreciate If I can get some answer.

Sandeep