I hurt my nose badly opening my car door. It's somewhat tender after 3 days and I have a slight headache. No bleeding or breathing trouble.?

Contused or broken. You may have broken your nose, but if it is not bothering your breathing, i would suggest that you only need to take tylenol (acetaminophen) or advil for the pain.
Nose. If your nose isn't deviated and the pain is decreasing I wouldn't do anything. Its probably just bruised.