Grape size lump swelling under the jaw at ear little pain in the morning (15min) and whole day without no pain and swelling what is the cause?

Lymph node. Possibly a swollen lymph node that has be filtering some sort of infection/ inflammation above the jawline, get an evaluation with a dentist or physician!
Lymph node. Possible localized infection that had quickly resolved is one possible option. Definitely track the occurrence and duration if it happens again.
Grinding teeth? It's hard to say for sure and the lump confuses matters but generally having pain on waking up in the jaws or a headache on waking is associated with grinding your teeth - which is generally done while we are sleeping. In any event, because of the lump, you need to see your dentist - try to make the appointment first thing in the am since that's when it seems to be worse!