one possibility for sudden excruciating foot pain (usually the big toe is the most painful) would be gout. assuming you are not having muscle cramps a spider bite or an injury this possibility would be high on my list. you would need to see your medical provider right away so that you can have a simple lab test. if your medical provider feels that you do have gout this can be promptly treated and you can get some immediate relief.
i woke up this morning with an excruciating pain in my foot. it is painful to touch and is hot to the touch. not a cramp. there are no marks or bruising. it feels like someone stomped down on it or like it may be broken. it gets really painful and throbs then it eases up a little but it doesn't go away.