You nicked a small blood vessel. It occurs sometimes and is not a concern.
The first shot went smoothly with no mark left behind. The second one caused only slight discomfort and a bruise showed up by the next morning. I am putting it down to not having much practice giving the injections myself but wanted to check anyway. Could the product be the reason even though the liquid looks completely normal and clear? I am probably worrying for no reason but would rather be safe.