If it is sudden then it is due to some allergy. Take antihistamines and review for adverse effects whatever medications you are taking.
If you have chronic symptoms then you have to rule out diabetes. Go for blood sugar estimation and also check your blood pressure and hemoglobin levels.
If all your vitals are fine and you have no diabetes then change to proper footwear and do some ankle exercises.
Finally if it does not solve your problem visit a neurologist for proper diagnosis and treatment.
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