Has there been any injury at the spot in the past? Was there ever a boil in that place? Have you ever sufferred a Herpez Zoster rash on the area? Have you been a diabetic?
Beacuse these are the organic causes of a numbness which is caused by dysfunction of the local nerve supply of the area.
On the other hand it may also have to do with the concerned nerve root getting compressed at the level of spinal cord.
I would like if you posted some more detail about the history and other features.
Dr Apurva C Madia
Consultant Cardiologist and physician