Hello...  This is Dr.  Pavan.  Glad to answer ur query.  The Corns on the undersurface of feet are caused due to some abnormality in walking or in the footwear.  There is high chances that if the Corns are not treated in its earlier stages,  it might get deeper and cause more problem and pain while walking.  The soaking in warm water and rubbing will give only symptomatic treatment and not treat the cause.