What is the ruling on reciting the chapter after Al-Fatiha and what should a worshiper who forgets it do?

Any part of Quran that a worshiper reads after Al-Fatiha during the first and the second rak`as [cycles of prayer] is a Sunnah, and forgetting to recite them does not nullify prayer or require making sujud as-sahw [prostration of forgetfulness].
And God the Almighty knows best.