Pain at the injection site is very common, especially if you are new to using gear. Long esters like cyp tend to be less painful than prop, but they still can hurt. Oil based gear is a "depot". After your injection, it sits in the muscle and slowly breaks down, releasing into your blood stream. This is a foreign substance and can cause pain, but the more you do it, the less it will hurt. Getting better at injecting will help though. Keep the needle steady. The more it moves around, the more damage you'll do. Also, be sure to inject very slowly, so that the oil doesn't shoot into the muscle with a lot of pressure. Also, if you get some blood into the muscle, it seems to "work" itself in a little better. So going for a walk or doing light cardio after a glute shot may make the pain go away a little quicker.

Gen Shi is known to be on the higher end of quality, but in the future, you can always try a different brand. I have found the Geneza line to work grat for me, and with much less pain than other popular brands. 

So rest assured, your gear is fine. This is just all part of running AAS. Be thankful you didn't decide to use prop for your first cycle ;)