I Created a web app in SharePoint 2013, and a site collection as well. But when I am about to open the page I get this message:
Sorry, this site hasn't been shared with you.
Log in as an Site Collection Admin and give the user you're logging in as permissions on the site.
I made this same mistake and selected the two key users who would be administering the site in the future, assuming my domain admin account would still be able to log into the site.
In Central Admin, go to Application Management > Change site collection administrators.
Set one of them (primary or secondary) to yourself.
I've had the same problem. After I installed update for sharepoint 2013, I didn't run product and configuration wizard, When I run that then It was fine. Just run configuration wizard and try again