....but it is in the area of your levator scapulae muscle. It lifts your shoulder blade up and in. That muscle and its neighbours are often victims of overuse -- especially if you have poor posture (eg "rounded shoulders") to start. But don't take my word for it. There is no internet substitute to having a health professional look you over if it is causing you trouble.
Got the same problem a few times... Not sure if it is excatly the same, but if i play regulary with my other arm for 15-25min at the end of the training I have rarly problems in this area. Doing exercises for the back also helps for me, as well as stretching regulary after (and shortly before) the training and if possible every day... The physio I attend if I have problems asked me to have a hot bath (or take a sauna) to relax the "overused", stressed muscels. Sometimes you need a physio or doctor if you have a dislocated vertebra, which can also cause pain in this area...