A lump has developed on the left Collar Bone, has become pretty visible lately. Seems like that of the size of a lemon with the second half inside the body. Been close to 2 months now since I've started noticing it, lump itself could be much older and has not caused any pain so far. Not sure if  has something​ to do with the Thyroid condition. Haven't seen a doctor until now. Can you kindly suggest as to how this should get diagnosed / which doctor should I seek advice from? Thanks.