So not carpal tunnel:
Carpal tunnel syndrome (CTS) is a medical condition due to compression of the median nerve as it travels through the wrist at the carpal tunnel.[1] The main symptoms are pain, numbness and tingling in the thumb, index finger, middle finger and the thumb side of the ring fingers.[1] Symptoms typically start gradually and during the night.[2] Pain may extend up the arm.[2] Weak grip strength may occur, and after a long period of time the muscles at the base of the thumb may waste away.[2] In more than half of cases, both sides are affected.[1]
However: cubit syndrome:
Beyond the elbow, the ulnar nerve travels under muscles on the inside of your forearm and into your hand on the side of the palm with the little finger. As the nerve enters the hand, it travels through another tunnel (Guyon's canal).
The ulnar nerve gives feeling to the little finger and half of the ring finger. It also controls most of the little muscles in the hand that help with fine movements, and some of the bigger muscles in the forearm that help you make a strong grip.
How do you sleep? face down with an arm underneath the body?