Hi, I Have A Lymph Node Above My Left Collar

Hi, I have a lymph node above my left collar bone that is larger then the other side..Not that large about a size of a pea.. maybe a little larger.. There is like a dull ache feeling in my neck.Sometimes i can feel a heart beat.. I have arthritis in my neck and not sure if its because of that..I was told by a friend its a sign of breat cancer.. What do you think?