How many times you pin that muscle? Which muscle did you pin? You could of hit a nerve. I hit one in my quad my first cycle I was hobbling around like I got shot for a week due to the immense pain.
I don't believe this is an infection due to it not being the redness or swelling. The anxiety is from you over thinking it. Give it time, keep an eye on it, don't worry too much. If flu symptoms, redness, itchiness,
or swelling occurs seek medical attention. But honestly dude i think you hit a nerve. Give it time and be careful to inject in the proper location.