My Podiatrist's Office Is Closed Till Wednesday. My Planter Faciitis

My podiatrist's office is closed till Wednesday. My planter faciitis hurts terribly. Can barely stand or walk. Should I go to urgent care facility? Would they be authorized to give me injection (cortisone)? Throbbing, spasm pain radiates all over left foot, upper calf. Foot swollen and tender. Spasms in right foot periodically. Unable to stand without use of cain