Must one repeat the prayer if the worshiper doubted the correctness of his recitation of a verse during it, then became certain of the error after finishing the prayer?

If someone makes a mistake in their recitation during prayer due to forgetfulness, their prayer is valid, and there is nothing against them. The proof for this is that the Prophet, peace and blessings be upon him, made a mistake in his recitation during prayer, and his prayer was not invalidated.

However, if the mistake is in Surah Al-Fatihah, such that it alters the meaning or omits a letter, then if the person corrects and rectifies it during the bowing (rak'ah), the rak'ah is valid. Otherwise, it becomes invalid, and it is obligatory to repeat it.