Since you are the admin of the site, I assume you have access to phpMyAdmin. If so, find the database (look for the name in the wp-config.php file), and use phpMyAdmin to access the wp-users table. If not, see below.
Find your admin user account in that table, and change the email address (I am assuming that the email address is not yours). Then you can use the ‘lost password’ thing to reset your password.
You could also edit that same user row in the table, and type in your new password in the appropriate field. Click on the ‘MD5’ button to properly encrypt the password.
Now you will be able to login as the admin of the site.
But, since you don’t have access to phpMyAdmin (the above answer part was for anyone finding this old question), then you need to create a new admin user. Assuming that you have selected the proper database, these commands ought to do that (changing values as needed):
INSERT INTO `wp_users` (`user_login`, `user_pass`, `user_nicename`, `user_email`,
`user_status`)
VALUES ('admin999', MD5('password999'), 'firstname lastname', '[email protected]', '0');
INSERT INTO `wp_usermeta` (`umeta_id`, `user_id`, `meta_key`, `meta_value`)
VALUES (NULL, (Select max(id) FROM wp_users),
'wp_capabilities', 'a:1:{s:13:"administrator";s:1:"1";}');
INSERT INTO `wp_usermeta` (`umeta_id`, `user_id`, `meta_key`, `meta_value`)
VALUES (NULL, (Select max(id) FROM wp_users), 'wp_user_level', '10');
I got this from here: https://www.hostpapa.com/knowledgebase/create-admin-account-wordpress-via-mysql/ . There are plenty of other similar articles to be found with the googles.
Of course, backing up your database before you start is always a good idea.