I clicked my wrist compulsively whenever I was Tired, Stressed or Nervous. I went to the Doctor's about it and she said I'd developed RSI (Repetitive Strain Injury) from doing it and it could seriously affect my work capacity and could lead to arthritis when I was older.
This scared me into stopping, but it was difficult to do. It can be really dangerous and damage your ligaments, whenever you do it slap you hand or pinch yourself to stop yourself. Then your brain will associate it with pain and if it's obsessive, it may stop. You may need to put a bandage on your fingers which will inhibit movement and heal the ligament your fingers.
Don't worry though, worrying will make it worse, it is easily curable. Hope that helps!
x