What Are The Holes On The Bottom Of My Foot?

I have four small holes in the bottom of my foot. It started with one. The one has been there for a VERY long time, not growing very much at all. Maybe a little teeny bit, but I don't think growing as much as a wart would. Now there's two that have been there for a while, and two more that literally just showed up in the last day or two (at least that I've noticed). They don't hurt or swell or anything. I tried freezing them off with home kits twice. Nada. I don't think they're warts beccause they don't grow, they don't hurt, and the freezing isn't working. What can they be?