I wouldn't be worried, it probably looks like a lot more than it is. If this happens a lot, I would look into performing your shots with the z-track method, it's meant to trap the fluid in the muscle because the "track" the needle follows is interrupted as soon as you pull the needle out and let go of the skin. It's pretty easy, you don't really need a nurse to show you if you know how to already administer your shots on your own.