Fingernail side is very painful may be trauma, lack of trace elements, nail groove inflammation and other reasons. 1. Trauma: If the nails are cut too short when trimming the nails of the hands, they are squeezed or caused localized injuries, which may lead to pain on the side of the fingernails. 2. Lack of micronutrients: If there is a picky eater, it may lead to unbalanced nutrition in the body, resulting in a lack of calcium and vitamins and other nutrients, which may lead to a painful fingernail. 3. Inguinitis: Inguinitis is an inflammatory reaction of the tissues around the nails, which may be caused by bacterial infection, and may result in a painful fingernail, accompanied by swelling and redness and other uncomfortable symptoms. Finger nail side very painful patients, should go to the regular hospital in time, clear cause, under the guidance of professional doctors to take targeted measures.