A few things make a wordpress site live:
1. Domain name that points to your server IP
2. WordPress install and database that is set to the same URL or domain name e.g. http://www.yoursite.com
If you hanged the URL in you control panel incorrectly that is why you cant login anymore. A fix is available directly in your wordpress database.
This can usually be accessed from your hosting control panel.
What is your doamin name/URL?
You need to check in the wordpress database that it matches.
See here for a similar discussion: