Is it mild swelling or severe? Are you under any treatment for
thyroid abnormality?
Of course a picture would help us to decode this situation. Try feeling the entire swelling with your finger and see If there's a boil anywhere in the swollen area and does it pain more when you press on any particular area. If the swelling is because of a boil then you need warm compresses, if generalized swelling and no pain/boil then cold compression may help
Next Steps
Look if it subsides naturally, do not use antibiotic until you have sent a picture/done a consultation and someone has prescribed it
Health Tips
check for any red small spot on the skin of the affected area, to rule out insect bite