How do i get rid of hard skin or corn on my feet?

There seems to be a spawn of hard skin or corn on my feet. These are the symptoms. They are small circular white bumps when at room temperature. But when the doctor froze it, it turned to this huge blister like bump. After getting it frozen, it hurts extremely much when touching it. So after a few days, i popped it, and it reappears. Anyone know what this thing is.