Hi, I Am Injecting B12 Lipotropic Shots Once/week In My

Hi, I am injecting B12 lipotropic shots once/week in my upper thigh, however, today I am pretty sure I injected it into a vein because it started bleeding immediately when I pulled my shot out and that has never happened before. I read some responses below for B-12 shots but these are the lipotropic shots and am not sure if I should I be concerned about this. I appreciate you letting me know.