Yes, once when my arm ached almost as soon as i left the surgery and the next day was totally black an blue - and I'm not exaggerating, from top to bottom, with a few 50p size patches of normal skin, it was awful.
It turned out, I've got jumpy veins, and so when the nurse stuck the needle in, my vein jumped and instead of the nurse taking the needle out and starting again, she kept the needle in and poked around for the vein, thus ensuring that she poked muscles and burst veins (hence the pain, and the bruises respectively). The pain was intense, I could hardly raise my arm to brush my teeth.
Not sure if this is like your pain, but it might be an explanation. The pain subsided within a week and the bruising within 2.
Hope you are feeling better, but I did go the doctors as I was really worried (got cream for the bruising IIRC). If you are at all unsure, go to the doctors, don't take anything for granted.