First of all taking antibiotics without any proper reason and without doctors advise is highly discouraged due to its side effects as well as it will increase antibiotic resistance which is already a problem in India. Throat dryness, fullness and irritation can be symptom of
thyroid disease itself. Other common cause is viral infection which does not require any treatment apart from rest, good hydration and nutrition and gargling, and it usually subsides by itself.
Next Steps
Kindly consult a general physician in person. So that your throat can be examined. If there is any sign of bacterial infection then probably antibiotic can be started.