Hello and thank you for asking!
I have gone carefully through your concern!
The lump you described may be infected and cause pain.
A careful clinical examination will determine the localization of the lamp, rather it is within or outside the thyroid
and some blood tests such as; full blood count, ERS and Protein C reactive will be also helpful.
After the above exams your treating physician will suggest rather to take antibiotics or to remove it surgically.
Hope the information will help.