Hi, Thanks for writing in. The finger tips are supplied by the median nerve and radial nerve. These nerves originate at the cervical part of spinal cord in the neck region and then course along the arms and forearms to reach the wrist and hands. These nerves have components originating from nerve roots of different levels which join together to form the nerves. It is possible that there is pinching of nerve roots near the origin or at any location along its route. Since the numbness is more on the middle and ring finger, therefor it is the median nerve that needs assessment. There can be trapping of the nerve at any point in its passage. AS it is happening for a week and is constant, please consult a neurologist immediately. You might also be required to do electroneurophysiological studies of your left upper limb. Rarely, a cause in the brain can be responsible for your symptoms.