I got lidocaine injections at the ER twice. It helped about 24 hours the first time & a couple of days the second time.
I imagine it would be much more effective for someone who isn’t having a severe adverse reaction to a previous injection.

I have done them several times and they have help but they are only a short term fix for me. Week to two week tops.

I did something called an occipital nerve block in the back of my head it lasted maybe 2 days. I even went so far as to have hollow qtips put up my nose and lidocaine pushed through the opening into my sinuses numbed the front of my face for 2 weeks. Did not faze my migraines.