I guess no permanent damage from drilling into a larger vein?

Injected on the left side and developed a hematoma, dark black and blue amount an inch square. It’s been three days and still there, maybe starting to fade. Never had this before. What did
I do?

So if I get a misfire, is it OK to inject again on the opposite side?

I usually get better results when injecting the right side. Is it really important to switch sides with each injection?