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If exactly one half of your body is paining it is possibly due to problem in a part in the brain. Do not take it lightly, get a Neurology consult. Avoid lying on one side much while sleeping, try to lie on your back. Is there any disturbance in sensations that you experience. How is your muscle strength on both sides of your body. Do not use the weak parts of your body much. For pain relief you can take
Paracetamol tablet.