The separation of the cat's chin from the skin may be caused by trauma. It is suggested to take the cat to the pet hospital for X-ray examination to see if there is any bone damage. If there is no bone injury, surgical suture can be considered to promote healing. At the same time, it is recommended to put a collar on the cat to avoid being scratched during the healing process. You can also try mixing some pet drugs with the water or food of cat Y. It may also be congenital developmental problems or mandibular hyperplasia or tumor compression.