Basically, you either made a subdomain name with “www.www” or you added a CNAME record with “www” to your subdomain name which already had www.
Maybe it looks like this in your DNS manager
www.www | CNAME | 1000 | example.com
or
www | CNAME | 1000 | www.example.com
Both of them will cause this issue, you should only have
www | CNAME | 1000 | example.com