What is good to use for deep skin cracks on knuckles and fingers?

Petrolatum. Super glue or liquid adhesives can provide some easy immediate relief. Using aquaphor, vaseline, o'keefe's working hands cream or other petrolatum based product can help to protect the skin barrier and promote healing. Try to identify the cause: overwashing with hot water, use of harsh chemicals or detergents can be the culprits.
Skin cracks. By the time itchy or dry skin has started cracking, a doctor's visit usually is necessary to diagnose the type of skin condition and start prescription treatment corticosteroid creams and ointments are often the first treatment; these drugs decrease swelling, redness and itch at the site, which allows the cracked skin to begin healing. Sometimes, topical or oral antibiotic is required.