Can foot numbness come from change in level of physical activity?

Yes: There are a number of factors that would influence foot numbness and activity level including pathomechanics, impingement syndrome, peripheral edema, shoe stability/fit/type, metabolic syndrome, repetitive injury, incomplete rest from previous injury. An examination is indicated.

Yes it can: You could be using muscles that are swelling and pinching on some nerve.See if it gets better with rest.