What could be the cause of the swelling between my neck and shoulder? Is that a place for lymph nodes?

Could be. Lymph nodes are all over the body. You cannot feel most of them but the head and neck area have many which can be felt and that shallow pocket above your collarbone is one area where they are appreciated. There are, however, other causes for swelling and depending upon your symptoms, if this doesn't go away see your doctor.