THere are no nerves in the region of the
coccyxTailbone (coccyx)
Tailbone trauma that supply that area. Potentially this skin area is supplied by the L5 nerve root which runs from the side of the spine down through the buttock into the back of the leg.
More commonly isolated sensory symptoms in the leg can result from local trauma to sensory nerves in the foot ie from tight shoes etc.
If the symptoms get worse and progress however I would have have it re-evaluated by your doctor.
Good uck