Unable to access admin. Warning error!

I put a code into the element.styleloader.php section about a week ago.That code modified the size of our heading text, the padding around that column, and the line height.
Today I made some modifications of that code, and then logged out of our dashboard.
When I went to log back in a few hours later, the message I got in place of the admin login screen was this…

Warning: Cannot modify header information – headers already sent by (output started at /home/content/c/o/l/colette2/html/wp-content/themes/super-skeleton/functions/custom-field.php:12) in /home/content/c/o/l/colette2/html/wp-includes/pluggable.php on line 876

My associate was already logged in as an admin, so I had her go to the custom-field.php section, but nothing was there that hadn’t been there before. We then noticed that this message would appear when any modification or posting was attempted for the site.

This message indicates that some code was put into the custom-field.php section right? But no one has done this. Unless it was somehow done on accident.
Also, Collette2 is the computer I was on when modifying my code earlier in the day.

At this point, we are unable to log into wordpress, or even get to the admin log in page, we only have access to the dashboard through my associates computer, which is still logged in, but totally useless.

I hope this is a clear enough outline of what the issue is. I’m a complete novice at this, and will definitely not be attempting to modify our site again. Haha. Can anyone help me track down where I’ve gone wrong? And if not, can anyone tell me who I can reach out to more directly who might be able to better assist me? Thank you so much in advance for any help!
Here is or site: http://www.newimagestudio.com