Had go nerve block for chronic migraines a week ago . feel pain has intensified since ? is this a side effect and does this mean im unlikely to get any relief from this procedure ? back of head is throbbing?

Greater occipital nerve blocks (which I assume you had), do not work very frequently, especially if done unilaterally, and many US neurologists use this rarely, if at all. Since arrival of the CGRP items, preventative therapy has become very achievable, but multiple approaches are now available. Hope the procedure you had works BUT other options could be employed

The pain you are experiencing may be due to hitting a nerve during the injection. Also the treatment you received may not have been appropriate for the problem you have. I would contact the doctor who gave you the injection and discuss your problem.