Hi Adalaide!
I am guessing that you've had your appt already? I'm not sure how much I help I'll be but perhaps the injection would help this area in your shoulder. Boy do I get the not liking needles. I too did a round of SGB and I've had some blow back from it too. Although I did LSB and no problems at all. Crazy. I need to try another injection (nerve root) but haven't been able to bring myself to do it yet. I totally get what your saying. I think it comes down to how much pain you're in and what you're willing to try to relieve it.. maybe? But in your last statement of not being able to afford a mistake... There are risks with any procedure, but imo cortisone injection seems like it would be a lower risk than some others like the SGB.
Just my two cents hon. I think it's such a personal choice. Let us know what you decided to do.