Could Collarbone Area Swelling Be Due To Cancer?

I HAVE RECENTLY BEEN DIAGNOSED WITH FIBROMYALGIA SO I PUT ALL MY ACHE AND PAINS ECT DOWN TO THIS NOW,, HOWEVER I HAVE HAD A SWELLING OVER MY COLLAR BONE AREA FOR OVER 2 MONTHS NOW.BOTH SIDES BUT MAINLY LARGER ON THE RIGHT>. HAVE HAD AN ULTRSOUND SCAN AND THE CHAP SAID LOOKED OK BUT MAY HAVE TO CHECK MY LYMPH NODES AS THEY LAY DEEPER.. COULD THIS BE CANCER OR WHAT QUESTIONS SHOULD I ASK MY GP TO CHECK FOR IN BLOODS ..CONFUSED