What causes the hard palate in the mouth to be so painful?

Nerve proximity: The hard palate is covered with thin mucosa over hard tissue and many nerve endings. This combination leads to a very sensitive and painful area when traumatized.

Duration?: How long has it been painful, is it constant? Is there swelling? Could be trauma i.e.Burn or a cut, abcessed tooth, periodontal infection. See a dentist.