Hello and Welcome to LinuxQuestions,
If you have access as root you could enter at the console with your root credentials and change the user's password with the passwd command:
which will prompt you to provide a new password. After that you can login with your regular user credentials.
If you also have forgotten that password (normally you provided it at installation), then you can follow a guide like this one:
http://www.go2linux.org/fedora-cento...sword-recovery.
Kind regards,
Eric