Yesterday I woke up and the pinky finger on my left hand hurt to bend and was a little swollen at the base of the finger (where the finger meets the palm of my hand). Today, the pain and swelling increased, and I also have stiffness of the finger. I didn't injure or do anything to my finger; these symptoms just started unexpectedly to just one finger/joint. What could be wrong? Do I need to see a doctor?