I guess the easiest thing to do would be to remove the hydrometer from your humidor for a few minutes (15 maybe) and let the humidity drop inside the humidor, and allow for the hydrometer to loose some of its moisture.

Try to space out the time you take to fill the hydrometer a bit longer, and you may want to switch to a different humidification medium such as the 65% beads that are advertised in the Marketplace right now.