Brief Answer: Too early to diagnose. It can wait till tomorrow Detailed Answer: Thank you for asking XXXX Sore swollen part right near neck on the back of head that sudden in onset, with no history of trauma and associated with difficulty moving neck is most likely a swollen lymph node of mastoid area with a likely possibility of mastoiditis. It can happen in many other possibilities like middle ear infection involving near by lymph nodes, simple neck muscle spasm can do that, parotid gland involvement like parotitis need to be ruled out too. infected Sebaceous cysts due to blockage of sebaceous glands or any other cyst may also present that way but the time frame in that case is a bit long. You can go the ER as it needs a bit detailed history and a complete clinical examination with some work up like radiological profile of this swelling and some needle aspiration if necessary and some blood work up and then it will be more easy to see what that is. Right now it seems too early to diagnose.you can wait till tomorrow too for a consultant opinion. Right now you can use some topical NSAIDs cream to help with some skeletal muscle relaxants to relieve neck spasm and help the movements like tizanidine or orphenadrine etc. I hope it helps.Take care and dont forget to close the discussion please. May the odds be ever in your favour S Khan

---