Missing support info - what XAMPP version and which Windows OS?
Did you delete the XAMPP index.php in the htdocs folder and replace it with your own index file or perhaps you deleted the XAMPP index.php in the htdocs folder and placed your own web site files in there?
You can't access XAMPP files and folders on localhost using your WAN IP as defined in the New security concept in the \xampp\apache\conf\extra\httpd-xampp.conf
file - but you should be able to access your own
web site files by http://my.wan.ip.address:8080/myown
index.php or http://my.wan.ip.address:8080/mywebsite.index.php
etc.etc. - but only you alone can test this issue out on your PC.
I could test if people out on the Internet can access your web site if you supply the IP address for testing but I and others on the Internet would not be able to access the XAMPP index.php file in the htdocs folder anyway, so that has to be deleted or renamed - if you feel it a security issues then after I have tested it and posted a reply you can edit your post and delete the WAN IP address if you wish.