Error shown when accessing wp site on add-on domain

I have main domain https://www.shreelekhan.com

On this domain I have added one “Add-on” domain from control panel. URL of add-on domain is : https://www.bdfrill.com.

WordPress version 3.5.2 is installed on it.
Theme I am using is ‘Responsive’ and I am working on ‘Responsive Child’ theme.

After installing, site was working fine.

Then I made changes in Settings > General > WordPress Address(URL) and Site Address(URL) by adding “www.”.

After hitting “Save” button, I am seeing “Oops! Google Chrome could not find https://www.bdfrill.com” message in browser

I am not able to access my site.

Kindly guide me further and oblige.

Thanks and Regards,

Tejas Gandhi