i have never injected in my quad before, and tonight i *tried for tha first time

i slipped tha needle in and as i was almost at tha point of how deep i wanted it, it looked like my muscle was coming to eat me, it jus popped out of no where, so i got scared n pulled out, what happened, i put it between 2 muscles, hit a nerve or jus jumped and didnt realize i flexed tha muslce?