When i wake up in the morning when i bend my fingers into a fist and then release my right index finger locks up. its the only finger that does, why?

Trigger finger: Sounds like a trigger finger. The tendon that bends the finger is swollen, and getting stuck as it slides by a guide called a pulley. Anti-inflammatory medicine like ibuprofen, naproxen, or Aspirin may improve it. A night splint can also help. A hand specialist can inject it with a cortisone type drug. Surgery is sometimes necessary. If it does not get better see a hand specialist.

Trigger finger: Most typically this represents a "trigger finger". There typically is no rhyme or reason as to why these occur. There is a pulley system that the flexor tendons travel through that can become swollen at the base of one of the digits and leads to discomfort in the palm throughout the evening this tendon is parked inside of this compressed pully or corset and first motion in the morning causes the nodule with in the tendon that develops to pop on one side of the pulley and then the other.