Problem with the betaferon injection

Hello, today i had trouble with the beta injector. My shot was at the bottom cheeks and when the injector started it stopped and a little of the drug was used. I tried by hand to put my shot but the needle came out sprying the drug and it form something like a knob. Very little from the drug was inserted. The knob dissapeared but this is happening to me for first time. Did i hit some underskin knob?
Sofia, Bulgaria