Thanks for providing more information.
As per your description,your symptoms can be related to nerve compression at cervical spine.
Sometimes repetitive strain,muscular overexertion can result in inflammation around nerves and puts pressure on their path causing pain,tingling,numbness sensation.
So you should try massage with muscle relaxant ointment on back of neck.
Also take OTC Advil.
Physical therapy can be advised.
In my opinion,as you are suffering from last few weeks so a consultation of your family doctor/chiropractor,Orthopedist should be considered.
Take short breaks while doing work.
Avoid putting pressure on your arm while sleeping.
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