I just got the "pen" injector for my infusion sites and I have little bruises where I insert.

I hurts way more than when I did it manually, but I like that I can do my back by myself.

Is the bruising normal?

back in the day when i was the pen i used to bruise a lot as well and in some cases bleed too. Maybe try a meatier part of your body that used to help me with not bruising.