I get numbness and sharp pain and high temperature...

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Regarding what you mentioned, the combination of numbness, pain and hotness of the upper back, neck and one of the arms , so this rise the suspicion of the presence of the herniated disc of the cervical vertebrae.
The herniated disc will compress the nerves that supply the upper limb at their origins from the spinal cord resulting in the previous symptoms.

What are the other possible cause?

This may be due to the presence of the rheumatologic disease , history of trauma to the cervical region or the presence of severe muscle's spasm.

What should you do in this condition ?

We advise you to take simple analgesic medication such as Ibuprofen tablets, you have to avoid further physical exertion which may exaggerate the symptoms you have and we advise you to visit the orthopedist doctor so that the doctor could do a full clinical evaluation of your case in order to determine the exact cause of this case.
  Stay well.   
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