hello there.thanks for writing to hcm.i have read your query and understand that you are suffering from pain from what you have been mentioning,i would say diagnosis would be pointing to injury to the deltoid muscle more than the biceps because the range of motion you have described to be painful is more of a deltoid action. have you had any history of trauma in the past 1 year?do you workout and what is your job nature,does it involve lifting weights?do you take any medications especially cholestrol lowering drugs like statins ? to get a more conclusive diagnosis in the case of such a pain involving muscular injury,mri would be advised of both the arm and the shoulder if you were my patient. Small tears and pulls would heal on its own,given adequate rest and supplementary therapy. basically,i would advise you to -rest and restrict the range of motion causing the pain -avoid lifting weights -have a good diet rich in quality proteins of natural source. -you can apply warm compress over the area and also apply analgesic gel like aceclofenac or diclofenac over the area.apply them gently only -you can also take tablet aceclofenac and thiocolchicoside twice daily for a week. All the above measures would provide relief slowly but surely in case of a muscle tear.If the tear is major,then surgical repair will have to be done. it takes time to heal,once pain starts to subside you can start physical therapy exercises with mild movements. hope i clarified your doubts.please followup in case of doubts wishing you a fast recovery.good day