if you were in a vein it wouldnt have been hard to inject, i know from experience when i accidently forgot to aspirate while doing a delt shot on my friend, he complained half way through, so i pulled back curiously and blood rushed in fast, scary shit, he had some heart pains later in the day(no lie). you must ahve been trying to inject in scar tissue, causing it to be hard, and the blood was from passing the needle through a vein, and it is not a worry... just apply pressure and massage lightly after the shot, as you should always do. peace