What causes pain like pricking by pins and needles in the middle left finger?

Carpal tunnel. It is usually because of nerve entrapment syndrome. Can be because of problem at wrist or neck. Sometimes hormone and electrolyte anomaly can cause. Vegans, females with repeated pregnancy and alcohol abusers can have it because of B12 deficiency.
Nerve problem. Carpal tunnel is one cause besides many other. See your doctor.