Of course, cracked heels can be from a fungal infection, or as a result of dry skin or psoriasis, but I have a simple solution for you to try for 2 weeks first.
-shower or wash your feet in warm water for 5 mins
-rub Vaseline into the area for 2 mins
-put cotton socks on and sleep with them on
Try this for 2 weeks and if there is no improvement, see a dermatologist.
Dr Ilsiphe Brown can be conatcted on 021 4182048