Hello, A possible explanation would be trauma from biting your cheek. You could grind your teeth at night and catch your cheek. You may damage the tissue and have some bleeding. Any difficulties with your bite with sharp edges or broken teeth? Any recent changes such as dental work, change in health care products, diet that could cause an allergic reaction? Rinse the area with warm salt water and continue to monitor for changes. If you repeat the trauma, that could explain the increase in size. I suggest you consult with your dentist. A clinical exam would provide you the best diagnosis. The concern is to rule out a serious condition such as a cancer. There are other infections possible and once diagnosed, medication may be an option to improve the condition. Your overall health needs to be reviewed with your dentist as well. Changes to your health, medications, diet, dental health etc. all need to considered. Keep proper oral hygiene, good nutrition with balanced vitamins, and stay hydrated. Thank you for your inquiry. Please consider providing additional details after you have considered my suggestions. I hope that I have provided helpful information and would be glad to answer additional questions.