I think as has been said, you are fine, but I think your thyroid has been 'excited' by the iodine. Just enough to get a reaction, but not enough to do much good.
I, too, had the tight, swollen feeling throat. I did eventually up to 50mgs, then100mgs before I saw much improvement. Also, lots of Vit C and Sea Salt to help with detox. Some also recommend to take breaks, maybe five days iodine, then two days off. For me, it worked better to just stay consistent and dose every four hours.
EVERYONE IS DIFFERENT. You have to see what works for you, but I honestly think you just 'woke' the thyroid and that is why you're experiencing what you are. I would advise to stay constant for at leat a week or more, before trying something different. Allow your thyroid to realize you will be giving it what it needs on a consistent basis.
Also, drink plenty of 'good' water to keep flushing the toxins out.