I have had a numb spot on my back for a while, the skin now hurts?

Neuralgia, perhaps: It sounds like something is affecting a superficial nerve that can be sensed as either a numbness, tenderness, or some similar sensation called paresthesias. It is a bit unusual, would need more history and a good physical exam, including basic neurologic exam, to assess and determine if more test needed. If symptoms persists for a month, would have it checked