Soreness from armpit to arm area may be caused by the following reasons. Firstly, it may be caused by the accumulation of lactic acid in the shoulders and arms after doing strenuous exercise or prolonged heavy physical labor, which results in the formation of soreness, and the pain will naturally be relieved after the lactic acid metabolism is completed in 2-3 days. Secondly, it may be caused by frozen shoulder, usually in addition to the above symptoms, it can be accompanied by widespread pain around the shoulder joint, and there is also shoulder joint dysfunction or pain will appear or aggravate when the shoulder joint is moving. Third, it may be caused by cervical spondylosis, degenerative changes in the cervical spine, such as osteophytes, herniated discs and other conditions that compress the nerve roots of the upper limbs, can also appear in the armpit to the arm of the nerve tugging pain or aches and pains, etc., but this condition is usually combined with neck pain, dysfunction and other manifestations of activity.