Child theme disaster

I have been working on designing a site in the theme Customizr to a temporary domain, today I decided to install a child theme to this parent and and accidentally messed with the functions file and now my whole site has gone blank!! I try to login and it just goes to a blank page and I cannot access anything in the admin WP ?? HELP, How can I access my site to disable or delete the the child theme or undo the mayhem I caused ??? I hope I didn’t wipe out the entire site, I am hosted through godaddy