The inside of my foot is swollen and it hurts when i wear shoes and when i walk and run. what could it be?

?tendonitis: If you have had no injury or new footwear, then plantar tendonitis or fasciitis

Foot swelling: Foot swelling is a sign of inflammation/injury. A stress fracture of a foot bone is a common cause. Other possibilities include tendonitis,arthritis,ligament injury. I recommend that you consult a podiatric specialist or orthopedic surgeon for diagnosis and treatment.