According to your sign and symptom you are suffering from pain in the muscle avd bone of shoulder.
As you know that best treatment depend on the correct diagnosis and correct diagnosis depend on the complete history of the patient so please take consultation from a doctor and give complete history of the patient so that correct diagnosis will be make and then best treatment will be start
Next Steps
it can be a case acute allergic contact dermatitis due to some infection.
Health Tips
Take any medicine after taking consultation.