The first thing that comes to mind - is the earlist stages of shingles (medical name: Herpes Zoster). This condition is caused by a recurrence of the chickenpox virus which hides out in the dorsal root ganglia, years after your initial infection.
In many patients - the first symptom is a burning type pain, hypersensitivity of the skin, and then it is followed by a rash - blisters. If you have blisters anywhere on that side - the diagnosis is bascially proven. Otherwise - it is more of a hunch.
If you have blisters now, or develop them - contact your doctor immediately and they can start you on Valtrex to prevent the pain from continuing long after the rash clears.
http://www.valtrex.com/shingles/whatis_shingles.html
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