I have been experiencing some moderate to severe pain that radiates from my right side of my upper back (shoulder blade) upper arm, under my arm and to my chest area. The pain is a stinging, pain that has not stopped since it started about 4 days ago. It feels like pins and needles at times, but it hurts to the touch almost like sciatica but in my upper right arm, chest and back.
Hi I am Chat Doctor. .  In my opinion it may be a kind of muscular spasm due to heavy lifting, vigorous movements or even wrong sleeping postures.  You may begin with avoiding such movements, overstretching and extending your elbow sometimes an arm sling is helpful.  Usually it resolves simultaneously within the first week but may extend to 2 weeks according to the trauma or injury severity. For my patients I recommend NSAIDs painkillers like Advil tab when needed, hot massages with topical gels will be ok if not you may need MRI to exclude any kind of nervous injury in your spine or shoulder for proper evaluation and treatment. Please consider a 5-star rating with some positive feedback if the information was helpful. Wish you good health, Any further clarifications feel free to ask.