Hi ! Have you changed your shoes/foot wear recently following which the lump appeared on your sole ? Most likely it has formed a bursa(cyst
like cavity near the bone) which got infected by repeated/chronic pressure while walking and started causing pain. If so, you may have to go for a properly fitting foot wear, take some anti inflammatory and antibiotics on consultation with your family physician. He may also advise you to go for an incision and drainage
if it has formed an abscess
. Also please get your blood sugar tested for exclusion. Wish you an early recovery.