Palatal injection Excruciating pain! Is it normal?

Two days ago, I got a root canal on one of my chewing teeth in the back of my mouth. I received shots to numb me, including one in the left corner of roof of my mouth. It was extremely painful, but after it took effect, I got through the procedure. It's been 2 days, and I'm experiencing excruciating pain; the pain is worse than the root canal site itself. When I drink water and a little bit touches the area, it sends a shockwave of pain through my entire head and begins to throb immensely. This is the first time I've cried as an adult since I tore a ligament in my ankle. Is this normal? Please, give me advice. Thank you in advance.