Shaikh Bin Baz rahimahullah was asked:
If a person eat pork meat ignorantly, is there any expiation upon? What is this expiation if it is obligatory?
“There is no sin upon him as long as he did not know. There is nothing on him. It is only for him to gargle his mouth and wash his mouth and his hands. All praise is due to Allah. If he did not gargle or did not remember that he ate pork except after a while, then there is nothing upon him”.
[Fatawa Noor ‘ala Darb (24/109)]
Faisal Ibn Abdul Qaadir Ibn Hassan