First, stop all exposure to nickle in cosmetic jewelry, supplements and even some metal tabs in your clothing. When I see a patient with cracks on their hands and feet I usually think in terms of vitamin D, zinc, Vitamin B3 or B6 deficiency but these should be checked by a Naturopath since western medical doctors are typically not trained in nutrition or methylation problems but increasing your CBD cannabis or THCA should help reduce the inflammation and CBD topical cream is also helpful for healing the cracks as well as calming the pain. CBN taken at night can help with sleep and has an antibiotic like effect.
As well as treating affected areas, be sure and remove all inputs of nickle…gold jewelry, esp earwires. Also stainless steel cookware. Try a simple canna-salve on your skin.