All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
You should hasten to settle the debt of your father from his inheritance, and do not use the interest in doing so; rather, the interest must be spent on the general welfare of the Muslims or given to the poor and needy. According to the most preponderant opinion, the heirs do not benefit from it.
Ibn Rushd (the grandfather) from the Maaliki School, said, “As for the inheritance, it does not make the forbidden money lawful; this is the correct opinion which necessitates consideration.”
Shaykh Ibn Taymiyyah was asked in his Fataawa, "A man dealt in interest and left behind money and a son. The son knows about the condition. Does this money become lawful for the son through inheritance or not?” He replied: “...as for the amount of which the son knows that it is from interest, he must give it out.”
Allah knows best.