It could be a rotator cuff injury. Does it hurt when you lift your arm above your head? you should go see a physiotherapist.
IF IT IS YOUR RIGHT UPPER ARM AND SHOULDER, IT COULD POSSIBLE BE YOUR GALLBLADDER
The scientific name for your upper arm is the Humerus
Stinging pain and weakness in the upper left arm could be caused by muscle strain, nerve compression (e.g. from a pinched nerve in the neck), or conditions like rotator cuff injury or tendonitis. It is important to seek medical evaluation to determine the exact cause and receive appropriate treatment.
Talk to a doctor this could be a sign of an underlying condition.
To be sure if you have pinched a nerve in your left upper arm please consult a physician.
biceps tendon rupture, C5 radiculopathy, many, many more, need to see neurologist to localize
Shia Labeouf has a paw print tattoo on his upper left arm.
You did not state your age or physical condition. The cause could be anything from muscle spasms to a heart attack. If they do not abate soon, if they increase, or if they return, please contact a physician immediately.
Upper left arm. This puts it as close to your heart as possible.
Roy Keane has a cross on the upper part of his left arm (Upper arm outside of his bicep)
neck and left arm aches related to angina ,
waht can cause my left arm to cramp and numbness in my left fingertips