Editing after going through comments:
After looking at the plugins of Joomdle, I found out a user plugin named joomlahooks. This plugin changes the way you login to the Joomla site. there is a function named do_login inside joomdlehooks.php. Inside that function there is a redirect command
$moodle_user = JoomdleHelperContent::call_method ("user_id", $username);
// Do nothing if user does not exist in Moodle
if (!$moodle_user)
return;
$comp_params = JComponentHelper::getParams( 'com_joomdle' );
$moodle_url = $comp_params->get( 'MOODLE_URL' );
$redirectless_sso = $comp_params->get( 'redirectless_sso' );
Inside the configuration is saved MOODLE_URL data. You need to check what is fed in that data. If you are unable to log into admin just use phpmyadmin and search for MOODLE_URL.
What I understand is you have overwritten the database where user credentials are stored with your production db dump. If you are using Joomla 3 then you need to check this table #__users where all the user credentials are stored including those of Super Users. You can filter by name Super User in your phpmyadmin. There you can change the username and password. Remember the password is md5 encrypted. So you can use some external website and generate the password. Once done try to login with new credentials and hopefully you will be able to login with your new credentials.
