"If you paint an area does it get darker after some time?"
-I woulnt paint every day, rather every 2-3 days. If discomfort have some oil on top.
Or paint different areas, close to the target, to avoid the burning effect.
I use to paint in the evening, then the spot is gone by the morning.
Antidote to Iodine on skin, lets say you want the spot to go away; ascorbic acid or borax; take away any mark from iodine.
In seconds ascorbic acid, a minute with borax.