SA ENT surgeon I can tell you this maybe due to 2 reasons
One is due to enlargement of mandible And other is hyper trophy of the masseter muscle.
Is the swelling is hard or soft to form in consistency you have not mentioned this
This both problems can be treated easily and you can get rid of this issue
Next Steps
Feel free to consult with detail history and image
Health Tips
An image of your face will be very helpful in diagnosing the disease