Hello, Your location indicates you may feel the movement of the mandibular jaw. You could feel the condyl moving at the TMJ which would explain why it disappears when you open. There is also a disc that slides between the joint and could be displaced. The angle of the mandible also moves as you open and seems to disappear. You should be able to feel a similar area on both sides of your face. If you feel this symmetry with no other symptoms, I would not worry. A Dentist could examine this area for you. If this is only on one side of your face you may have a cyst, swollen lymph gland, growth, pocket of infection, acne or deep pimple. You can visit a dermatologist for a clinical diagnosis. If you develop other symptoms, please see a doctor. Diet, other medications and products used on your face and hair could contribute as well. Caffeine is an accelerator and can affect the body. You can easily control your intake to evaluate for yourself if this has any effect. Are there any additional details you could provide to help with a diagnosis? Other medical conditions? Medications? Dental health? I would be glad to answer any additional questions. I hope my discussion is helpful and that the area resolves without any further complications. Thank you for your inquiry.