Cannot Access WP-ADMIN after modifying wp-config to fix SSL redirects issue

My site recently was upgraded to SSL and was facing TOO_MANY_REDIRECTS error. Managed to solve that problem by, enabling ngix and the wp-config.php snippet below.

define('FORCE_SSL_ADMIN', true);
define('FORCE_SSL_LOGIN', true);
/** Forwards HTTP/HTTPS status, and visitors’ true IP to WordPress on Optimized Hosting for WordPress */
if($_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https'){
$_SERVER['HTTPS'] = 'on';
};
if($_SERVER['HTTP_X_REAL_IP']){
   $_SERVER['REMOTE_ADDR'] = $_SERVER['HTTP_X_REAL_IP'];
};

Once that was done, my access to WP-admin was disabled, meaning I can’t access it like I used to.

This is the error I’m facing:
PHP Warning: Cannot modify header information - headers already sent by (output started at /home/plantoos/public_html/mag/wp-config.php:1) in /home/plantoos/public_html/mag/wp-includes/pluggable.php on line 1207

Do anyone has a clue to this? Your help would be greatly appreciated.
Thank you!