It's not because the nurse was rough, it's because the intramuscular injection creates a pressure inside the muscle where none has ever been before, so it takes time for the muscle to adjust.
It can take about as long as a bruise, cause it kind of like a bruise on the muscle itself.
For me, I am sometimes very sore (up to "it hurts to move!") for up to 2 days after my shots, and a little bit sore to the touch (that is to say, can't put a lot of pressure on it cause it kinda hurts) for up to a week after.