Hi
Welcome to the MedHelp forum!
It is difficult to comment without examining. The tongue could be cracked due to various reasons. It could be due to iron deficiency anemia, pernicious anemia and other B-vitamin deficiencies, aphthous ulcers, oral lichen planus, erythema multiform, pemphigus vulgaris, syphilis, yeast infection; exposure to irritants such as hot foods, or spices, tobacco, alcohol; allergy to toothpaste, mouthwash, breath fresheners, dyes in candy, dentures, food items, coloring agents, or blood pressure medications like ACE inhibitors. It could also be a mechanical irritation by a jagged tooth edge or a denture. Gastric reflux could also be a cause.
Please discuss this with your doctor. Maybe you should also have a dental checkup. Go over the list, something may strike you. If you have IBS or other gut problems or a poor diet then any deficiency could be the problem. You can take a multivitamin pill but it would be good to know the exact cause before starting any treatment. Take care!
Try a homeopath if traditional medicine can't help you.