Why did one side of my cheek become very noticeably deflated?

If you have facial volume loss there are many options such as fat, fillers and implants. I suggest you see a cosmetic dermatologist with experience.  Best, Dr. Emer.

 It is likely that you had a fracture of the maxilla bone on the right side. This bone provides support to the cheek area.  If the bone was fractured it may not be supporting the cheek tissue the way that it did before the accident and this may cause a flattened appearance. Depending on your specific situation, this might be corrected with A cheek implant or fat grafting or bone grafting. contouring procedures.  Best regards

Hello Shellyp1029,Sorry to hear about your accident.  The most common reason for the cheek to look deflated after an accident like this is a fracture of the cheek bone itself (called the zygoma or zygomaticomaxillary complex).  This long out it would be difficult to fix that bone into a better spot.  Because of that, you are looking are ways to camouflage the area.  This may be done with cheek implants, fillers, or fat transfer depending on the degree of augmentation needed.  I would recommend you consult with a facial plastic surgeon to go over your options.  I hope this helps and good luck.