Most probably you have infection in nasopharynx
(upper part of throat) causing you pain there. There must be some inflammatin in lower parts of throat due to above said infection. That is why you feel comfortable when you take warm things.
Swelling below your jaw is due to lymph gland enlargement. This is because of inflammation in that secondary to infection in your nasaopharynx.
Recurrent earache is due to what is called as 'referred otalgia'. That is without any problem in ear you feel pain there through nerves also supplying nasopharynx or swollen lymph gland
Except for earache you have not mentioned any other problems of ear. So I assume it is a referred otalgia. But it is important to make sure by examination that no problem is there in your ear.
Earlier hemithyroidectomy does not have relation to these.
Your problem has been going on for 10 days. That means your immunity is unable to overcome the infection. So you will need a course of antibiotic and pain killer if earache or throat pain is troublesome.
Please consult an ENT specialist
Wish you good health.