welcome to health care magic..
is a mobile sweeling that means it is freely movable and is soft,,so in the query your's is not lipoma...
feel fot the swelling with the back of your hand and compare with other body parts,,if it is hotter than the normal it is localised inflamation...and use antibiotics after consulting general surgeon
if it is not hot,,,then you require an x-ray of that to rule out any tumor
arising from the collar bone..
don't waste time,,simply consult your surgeon do according to him/her..hope you understand my suggestion.
have a speedy recovery..