Diabetic neuropathy. Uncontrolled diabetes can damage your nerves. If you have damaged nerves in your legs and feet, you might not feel heat, cold, or pain there. This lack of feeling is called "sensory diabetic neuropathy." If you do not feel a cut or sore on your foot because of neuropathy, the cut could get worse and become infected. The muscles of your foot may not work properly because nerves to the muscles are damaged. This could cause your foot to not align properly and create too much pressure on one part of your foot.
Peripheral vascular disease. Diabetes also affects the flow of blood. Without good blood flow, it takes longer for a sore or cut to heal. Poor blood flow in the arms and legs is called "peripheral vascular disease." If you have an infection that will not heal because of poor blood flow, you are at risk for developing ulcers or gangrene (the death of tissue due to a lack of blood).

Symptoms

Changes in skin color
Changes in skin temperature
Swelling in the foot or ankle
Pain in the legs
Ingrown toenails or toenails infected with fungus
Dry cracks in the skin, especially around the heel