What Causes Pain And Stiffness In Finger Joint?

My dad is 47 years old and recently he has started experiencing an unsual pain in his right ring finger especially near his palm. He says that when he fold all his fingers together and then tries to unfold them, then all fingers unfold themselves except for the ring finger and then when he tries to open it,it kind of hurts and opens slowly with small sound of like finger cracking. Not only that but also when he wakes up in the morning he finds his ring finger folded and hard to unfold and when he tries to unfold it, it produces a strange kind of pain in his nerves surrounding the finger. The pain exists until he immerses his finger in the water while slowly massaging it. Now he went to a doctor and he was told that there is a certain kind of meat flesh that has grown up near the joint of plam and the ring finger and therefore they will have to do a small 15 minutes operation on his palm where they will remove this flesh. However, he is still suspicious about it and asked me to find out more about this condition and here I am. Your help will be appreciated.