May Day! I modified functions.php but it just crashed my site

I’m brand new to WordPress and feeling my way around. I have a WP site under construction at https://www.consignmentreview.com and started out with the Twenty Eleven theme as the base theme. I am customizing it by building a child theme of twenty eleven called consignment review. I was trying to figure out how to change the max height of the header and after some research here discovered it wasn’t controlled by CSS or header.php but functions.php. Hmmmm. I changed it in functions.php, uploaded the change and “poof”; my site is broken with a database connection error. How do I get it back? Do I have to reinstall it?