A swollen cheek on one side of a dog may be caused by foreign matter, fungal infection, injury, etc. You can first check whether there are other hard objects in the dog’s mouth and help the dog remove them. Sometimes dogs conflict with other pets. It will also cause swelling of the cheeks. If there are obvious wounds on the dog, they should be wiped and disinfected with iodophor in time to avoid infection. During this period, you should pay attention to improving the dog's diet and try to feed some light food to promote the dog's health.