Hi Jennijojo,
I am excited for you and will send thoughts of healing and comfort. Since the block is stellate you could get the Horner syndrome that another recent poster had. It affects the eye and causes some facial droop. This is transient and doesn't happen to everyone. It means they hit the right spot though so don't panic if it happens.
Can injections to the hand have caused CRPS? Impossible to say, Anything can happen and injections can cause damage even when ultrasound guided. The steroid flare that you got may have been related to what steroid they used. Kenalog is notorious for crystallizing and causing pain. Others do it to a lesser degree but can still cause an issue. Did you let your doctor know about this? It may affect what they decide to use.
I hope this brings you some relief! Wouldn't that be wonderful news!
Sending hugs, Littlepaw