Cracked heels can be very painful, the symptoms are pain on weight bearing and thickening of the skin around the heel, this is called callous. Walking barefoot, shoes that are open such as sandals and thin soled shoes can make the symptoms worse. Thick dry skin (callus) can be due to the way you walk.
Treatment: Filing and creaming with a heel balm will help but a foot health practitioner can debride the area more successfully and use a skin glue, if necessary to seal the cracks. If the cracks become infected, then an antispetic cream needs to be applied.
Never use a razor or scissors to remove any skin.
I offer the option of a luxury paraffin wax treatment to aid in the prevention of further problems. £15