How can I prove that the head of the lab did not have contribution to my work?
Sorry, I don't think you can do much at this point. These things should be negotiated before any resources are shared. Nothing is free, and different people may expect different forms of gratification- reciprocation, acknowledgement, authorship. You are entitled to having your opinions about this, and the correct time to voice them is at the beginning of the labwork/collaboration.

It is possible that your advisor has a prior understanding with this lab that you are not aware of. If this is not so, share your misgivings with your advisor and seek to learn his/her reasons for conceding authorship. With that knowledge, you can avoid such a situation next time. 

This time, 'unblock' by giving credit.