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After going through your history headache on one side and clear fluid blisters strongly points to the possibility of Herpes Zoster
If you have suffered herpes in past you may be aware of the lesion.
I would suggest to visit a Dermatologist
or Physician and get it confirmed once it is diagnosed then proper treatment with anti viral drug like Acyclovir
may be given .
Supportive treatment include analgesic
,B1,B6 & B12 vitamins and local application of anti viral ointment.
Hope this information helps.
Dr.Akhilesh Dubey M.D.