What Causes Pins And Needle Feeling With Numbness In Arm At Injecton Site?

Hello,
I am an IV drug user who understands all risks & takes every precaution possible to avoid complications. I am new to using the backs of my hands & I am concerned I may have hit my ulnar artery earlier tonight.
There was already blood in the syringe so the colour of my register was difficult to assess, I did notice it was lighter. It registered strong but not enough to push the plunger, I still had to pull back. There was no pain injecting at all. There is no swelling anywhere in my hand/arm/injection site. I do have minor pins & needles in my fingers & a slight numbness in my forearm but I also suffered a severe neck injury in 2008 so this is nothing unusual for me.
Is there a way to tell exactly what I hit? Does it always hurt if you inject into an artery?
Thank you!