hi, welcome to HCM I am Dr. Das
So, you have cervical and probably left supraclavicular lymphadenopathy
Now, to be frank, on left side both cancerous and non cancerous cause. Which include ifectious conditions alongwith some carcinomas.
You did not mentioned what type of thyroid
lesion you have.
Now,first you have to do FNAC from those lymph nodes . It is must. If it becimes noncontributary then surgical biopsy