Do you have any dental infections that you're aware of?
I'm only asking because the same thing happened to my partner about 3 days into Iodine (he does 2 drops of 7%) and he has an impacted wisdom tooth that was infected on the same side as the swollen gland... After having the molar and wisdom tooth extracted the swollen lymph node went back down. It's still a tiny bit swollen, but his wound is still healing.