Are you serious? The whole point of aspirating is to ensure that you ARE NOT in a vein!!!
This is supposed to be an intramuscular injection, not IV. Did you do ANY research before starting this?! You could have killed yourself, since the oil would hit your brain and starve it of oxygen (possible, had you injected the full 3ml). This is called an embolism.
We aren't ****ing with you. You really did that wrong, but since you didn't die on the spot you'll probably be ok (but that area will be sore as all hell for a week).