For under active thyroid go immediately (don't pass go) to the Iodine forum. Almost everyone is Iodine deficient and the thyroid is one of the first things affected. Goiter can usually be completely cured by supplementing Iodine and occurs in areas of greater iodine deficiency (usually inland).
I put a few drops of Lugols iodine in my thermos every day. Increases energy levels too.
As for healing crises with coconut oil - it could be. Coconut has strong antibacterial/viral properties and can stir the pot but also bring on the healing. It's also possible that you have some kind of allergy to the stuff. So if after some more attempts the throat swelling doesn't stop or gets worse, switch to another oil and see what happens.