Causes of inner bunion split include trauma, gray nails, onychomycosis, and nail psoriasis, etc. Treatments such as medication and surgery should be given according to the causes. 1. Trauma: If trauma is the cause of a split on the inside of the nail cap of the bunion, surgical treatment such as debridement and suturing can be given. 2. Gray nail: If it is gray nail, then you can give terbinafine, itraconazole and other drugs antifungal treatment. 3. Inguinitis: For the cracks on the inner side of the nail cap of the big toe caused by inguinitis, it is necessary to give levofloxacin and other drugs for antibacterial treatment, and if necessary, give surgical treatment such as nail extraction. 4. Nail psoriasis: For patients with nail psoriasis, it is necessary to give methotrexate, cyclosporine A and other drugs for anti-immunotherapy. The phenomenon of cracks on the inner side of the nail cap of the big toe should consult a doctor in time, and standardize the treatment under the guidance of the doctor.