The goitre WILL actually swell with Iodine intake to capture as much Iodine as possible in insufficent states. This is in the literature if you look for it.
I had a goitre too... a massive one.. which was removed.... I was left with half a thyroid which was growing another goitre.
I used the Iodine for 3 years and was able to shrink my goitre and halve my meds. Often, the iodine defiency will come from having Ascaris infection and/or insuffient iodine in the diet, which is almost everyone.
Initially there was swelling but I persevered. You may want to reassess. xox Good luck.