Thanks for your query.
Most probably,you might have acquired Upper respiratory tract
infection. Because of infection and inflammation,there may be difficult in swallowing.
Please consult your doctor and get examined.If it is due to infection,it will be subsided with Antibiotic and Anti inflammatory drugs.
As you got treated for thyroid cancer
,please get checked whether any recurrence has occured or not.
Hope it is a minor infection.
Wish you good health