Most likely, in the absence of other symtpoms, you are experiencing swelling around the eyes (periorbital edema) and face because of your salty dinner. The sodium load causes you to retain excess free water, and with the aid of gravity, it pools in the dependent parts of your body. During the day, it would be your feet, but at night, when you lie down, your face will also become swollen. The swelling is usually transient and should resolve within a few hours as gravity helps drain the fluid from your face and your kidneys work to excrete the excess sodium and free water. To prevent the facial swelling in the future, avoid eating salty foods before taking a nap and prior to bedtime.