Morning - you do not need to wash an area before you inject unless you have a physical job that makes you filthy and you need to shower after work. For the average person, which I know you already know, swab the vial, swab the injection spot, and if using good gear and a clean needle, you should be fine. I have been injecting for decades on and off with TRT or with a mild cycle and this system has never failed me yet.
Accidents happen and you drop the needle/ the needle touches something accidentally. If that happens, I screw off the needle and replace it. I am not arguing with you - it could be the soap but if you take rubbing alcohol (I find 70% best) and you clean off the skin well, you should be fine.
Is it any better or the same? Is this the first for you in years or has this occurred before with specific carrier oils?