Why does moisture cause pain behind glans?

I'm trying to understand why a bit of moisture causes some pain and soreness behind the top of the glans? I put mine on right out of the shower today and have had a bit of discomfort behind the glans for the first time today. I saw a few posts commenting on this so I was trying to understand why something as simple as a bit of moisture causes it.

Does it mean you just need to really dry off before putting it on? Is there anything you can do about it if you're locked up for the day already?