A number of people have reported burning with Lugol's. I've heard the figure of 20% of people taking 50 mg or more Lugol's.
Some people have had to stop for a month to heal the esophagus or stomach. Iodoral is designed with a glaze to digest further down in the gastrointestinal tract in order to avoid stomach burning or upset.
Let us know how long it takes to recover. Sorry you had to go thru this.