Pay attention to how you are holding your foot while driving, if it is only the the gas pedal foot. You may be holding your foot too tensely. I realized I was doing that in stressful traffic.

Stretch your feet. You can buy foot stretching gizmos that you can sleep in, but there are some really good yoga foot stretches too. I have a friend who is into yoga in a big way. She showed me a stretch that invovled squatting on the balls of my feet, hands on the ground in front to support the body, with the toes spread as widely as possible. She would often do it on the edge of a step so she could really stretch. At first it hurt and I couldn't stretch far, but little by little it got easier and my pain went away. Mine was caused by standing on my feet all day on concrete, and a change of shoes helped to. The short periods of ice and stretcihng helped the most.