You can try one of the following two solutions
1.
You can use phpMyAdmin (or a similar DB administration package) and look in (the technical term on the link is "browse") the nuke_authors table. You can take two approaches:
1.
See if your admin is still there, and you can set a new password (you'll have to choose "MD5" from the dropdown menu on the pass field). If your admin is not there, then just add a new row to the table and put in the missing info.
2.
Or you can just delete the line with the administrator name and point your browser to the admin.php file - you will then be prompted to enter a new admin name and password. You may enter whatever new values you like there, but you should not create a user with the same name, even if prompted to.
2.
Using phpMyAdmin (or directly in MySQL), go to the nuke_authors table and make your password dc647eb65e6711e155375218212b3964 - that will make it Password, then just login and change it. Here we make use of the fact that the MD5 hash of the word "Password" is dc647eb65e6711e155375218212b3964.