hi; Please give rest to your shoulder it requires rest.Exercise or work out is a strenous activity for muscles & occassionally result in internal injury and so the give us the message of injury in form of pain.The muscles are made of minute fibres ;a small fibre if breaks we can t know but internally it causes swelling & pain .These minute injuries also need time to heal so whenever there is pain don t exert that part .The treatment is to give max rest to the part ;you can take a anti-inflammatory like BRUFEN-400 three times a day if you are not allergic or asthamatic.take it for a week .Hopefully you may feel better in a week. thanks