The lesson is simple: Sometimes we need to see a professional.
Earlier in the day, a passenger had accidentally slammed a car door without realizing that my friend still had his hand gripping the door frame at the door hinge. Despite fast reactions, the door caught one finger and smashed it pretty hard. Now it was swelling up and throbbing; but he needed the license plates and figured he might as well get some errands done since he couldn't do much else, not even type on the computer to retrieve his e-mail.