Brief Answer:
needs evaluation, kindly give details.

Detailed Answer:
Hi
Thanks for using Hcm.

Pain and soreness at the back of the head, unilateral as in your case can be due to any,

Trauma or injury to that area or any local infection of that area causing neuralgic pain and soreness.
Any cervical neuropathy usually right sided.
Migraine
Variations in blood pressure.
Earache on the same side.
Improper position during sleep or incorrect posture pressurising that area.

Do you have any history of fever,neck spondylosis,pain in the right arm,hypertension, peripheral neuropathy, diabetes,hypothyroidism or migraine.

Any symptoms of vomiting, headache, blurring of vision,irritability or restlessness.

If the pain and soreness is persistently present it should be evaluated.

Kindly get back to me with the details and any relevant previous medical history.

Hoping to help you with your problem.

All the best, take care

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