Hormones influence the size of any lump (the lump isn't the same size all month).
Iodine does so as well: any lump will get bigger. This happens to me too. It happens in my breasts, but also in sun spots on my skin. When I put Lugol's on my sun spots, they get raised. After a while they disappear.
When I started taking Iodine internally, my breast lumps got bigger. Only then will they start to disappear. The lumps in my left breast are about 1/3 of what they started with, in my right breast thing are progressing more slowly.
So the fact that the lump gets bigger just means the tissues are reacting to the iodine: a good sign.