A few weeks ago I accidentally injected into one of the small veins in my thigh, despite pulling back on the syringe - I think I must have moved the needle tip as I pressed the plunger. It was a bit more uncomfortable than usual, did bleed a bit afterwards and I did have a small bruise but otherwise I had, and have had, no other effects. I knew I had done so as there was also some blood in the syringe.
I thought I would post this to reassure Peggylally66 and lots of others who SI. I didn't mean to but I definitely won't worry about doing it again.