Cannot Modify Header Information wp-admin error message

Received the following error message when accessing mywordpressblog.com/wp-admin:
Warning: Cannot modify header information – headers already sent by (output started at /home/content/77/6690377/html/wp-content/plugins/islidex/islidex.php:1170) in /home/content/77/6690377/html/wp-includes/pluggable.php on line 890

I understand that most likely the issue is that when I installed the islidex plugin that the wp-config php code was altered by adding a space somewhere.
However, how do I edit my blog php code without being able to log in to my wordpress admin panel via mywordpressblog.com/wp-admin? Is there a way for me to delete the plugin all together without loggin in to my admin panel?

Thanks