What causes pain in foot upon awakening?

Many things! Periostitis of the heel bone, plantar fasciitis, morton's neuroma, gout occurs in the morning, but attacks usually last longer than you are implying. Metatarsalgia from arthritis. I can go on longer. See a rheumatology specialist, or a podiatrist, or orthopedic surgeon. Diagnose first, treat second. Good luck!