Hi Ehsan,
This is a very common error so don't feel too bad.
The license won't work at this point as it only works when it is associated to the MAC address of the CAM. You will have to contact the folks in Licensing at Cisco and/or the people who sold you the box.
If everything is legitimate it will take less time than you think to obtain a new license. Just make sure you have the latest software from CCO.
Hope this helps.
Paul