hello there! A tiny red spot on your foot which is tender should be evaluated since you are a diabetic. People with diabetes should be very much caring about their feet since any infection or injury could lead to diabetic foot which is very troublesome. Diabetics have their sensation altered in the extremities as a complication of diabetes which is called as peripheral neuropathy, wherein you might not be aware if your feet gets hurt while barefoot or when you get in contact with extreme temperatures. Infection is quite common as there s high levels of sugar levels in your body which acts as a favorable media for invective organisms to grow. You should consult your primary physician in person to get the red spot evaluated. He or she might suggest you some antibiotics and personal care. Hope this helps.