Hello, welcome to HCM, I am Dr. Das
Firstly, the swelling you described, could be a lymph
So, first you have to search for any infectious origin. If, the infectious origin is excluded then one Fine needle aspiration cytology should be done to rule out any metastasis from the previous thyroid
So, consult with your treating doctor for a thorough clinical examinaton and for ordering a Fine needle aspiration cytology from the prominent lymph node.