Post Botox: Sharp recurring pain at base of my skull on the side - it feels like a stabbing and last only a couple of seconds

Is this normal ? I had my second round of botox shots 2 weeks ago. So far I see no change in my headaches although with my first treatment I had 2 great months of more than 50% reduction in headaches. Last time I got relief after 7 days and it was remarkable. And, can I expect the botox to start working?