Self B12 injection - not urgent, just curious

I have been giving myself the B12 injection for many years now and this is the first time I had this.  The skin around the injection site (about a 2 inch area) is very pink.  I am EXTREMELY pale so things would show more under my skin, but I don't remember this ever happening before.  It's almost like I did not get the needle in deep enough.  Is that possible or does it matter with a subcutaneous injection anyway?  I just want to not short myself on the vitamin.