I have licensed for www.xyz.domain.com, the actual domain is xyz.domain.com is this a problem?

ANSWER

No, web site licenses will work with and without the "www" sub-domain. An additional license is not required for this case.

QUESTION

If you needed to use both xyz.domain.com and abc.domain.com then another web site license would be required (or a server license).  The web site license will work on the exact URL provided with and without the "www" subdomain only.