I cannot tell you how many times we've had someone post to this forum on side effects of Iodine supplementation when they've been prescribed iodine, and Iodine alone by some MD or ND or whatever. The doc never suggests companion nutrients and NEVER discusses "adverse" reactions, detox, or healing crises.
That includes the io-docs. I think that they're more educated now, but I remember in the early days one of Flescha's patients being told(by Fleschas) to "tough it out".
There are a bazillion web references on Iodine supplementation now, when this forum began, there were few. There are all sorts of docs on you-tube touting the benefits of iodine, there were none when we began.
My point is that your ND prescribed iodine in a very uneducated fashion. I think that we can correlate this to an MD prescribing a drug because the info that he got from the pharmaceutical rep said that it will work for such and such condition.
Iodine is "popular" now, and I'm glad for that, but, as usual, there are people running around prescribing when they have not done the most rudimentary studying themselves. That's the case with your ND. Fire him(her). And take responsibility for your health, because nobody cares as much about you, as you.
BTW, you'll be fine. Your reaction indicates that you need iodine, absolutely. You might be more comfortable titrating your dose up, slowly.