Could be lone of a few things: the AC joint (the joint between the collar bone and the shoulder blade or scapula). This mainly comes into play when the arm is elevate above the head. There are several ligamentous structures within the shoulder that could also have been torn and the shoulder could have subluxed as well (a partial dislocation) which can damage the joint and the humeral head.
Does it hurt at all to take the arm across the body to the opposite shoulder? Really should should book in with a good local sports physio for at least an assessment and advice on the way forward. Best of luck
