My thumbs develop painful cracks at the corner of the nails despite using hand cream. What can I use to keep this from occurring?

Soak, urea, liquid bandage. The skin is severely dry until it cracks open. For immediate relief soak thumbs until they are wet and then apply urea based cream sold for foot cracking. Another approach is after wetting skin is to apply johnson and johnson liquid bandage for immediate relief. You may have a contact allergy which needs to be identified by dermatologist.