Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services if you have severe difficulty breathing, feel that your airway is closing, cannot speak because of breathlessness, or develop blue or grey lips or skin.
Seek urgent same-day help for a neck swelling that is enlarging quickly, new noisy breathing, or rapidly worsening swallowing problems.
Arrange a routine medical appointment if you notice a new or persistent neck lump, an enlarging thyroid nodule, unexplained hoarseness, swollen neck glands, or ongoing difficulty swallowing.
These symptoms are usually caused by something other than cancer, but they should be assessed.
If you have been treated for thyroid cancer, contact your follow-up team if you develop a new neck lump, a lasting voice change, increasing swallowing difficulty, unexplained bone pain, or other new symptoms that do not settle.
And for anyone, someone who:
Every sign above is quoted from the sofidex article on Thyroid cancer. If you are not sure, err upward — it is always reasonable to be checked.