Based on this, I assumed the pain scale was something like

0 = I was unaware that receiving oral sex is part of the evaluation process, but thank you, nurse.
2 = The mild irritation of needing but being unable to sneeze.
4 = This is actually just ennui.
6 = The stupidity of your diagnosis would cause me to facepalm if my hands were not so badly burned at the moment.
8 = I've recently been smashed in the face with a cast-iron frying pan. How do you think I feel?...
10 = ...and now my eyes are leaking pimples on to my face as well. Dammit!