Unless it's under a callus I pop and cover the area. But I have great socks and shoes these days and haven't had many issues. I did get a small blister under the callus on the ball of my foot - thought I had a pebble in the shoe. It didn't hurt, so I left it alone, and eventually it went away.

I had a small abrasion turn into a foot infection that was starting to be a blood infection - had to have IV antibiotics daily for a week outpatient. It was all frontcountry, I snagged a sandal on a crack in a sidewalk and did a spectacular fall, the only injury was a tiny skin flap on the back of my heel. I still have a bump of scar tissue years later for my trouble. Keep 'em clean, folks. Irrigate with clean (filtered or treated) water and leave no doubt, get all the grit out. Triple antibiotic cream, gauze, tape it up, put a donut of moleskin around it if it's in a high friction area and check frequently. At camp and on breaks let it get some air and dry out the wound before cleaning it again. If it's developing a greenish tinge around the wound and the area looks red, get the heck out of the wilderness and get medical treatment.