Hi.i Have A Hard Lump In My Right Shoulder Above

Hi.i have a hard lump in my right shoulder above the collar bone on the flat part before my actual shoulder.i thought it was a knot in the muscle but it as hard as a rock.im waiting on xray results. My own dr was unsure as to what it might be.i cant lift my right arm fully without discomfort.the lump isnt sore just more annoying at times. What could it be?