What one will do to remove any najis thing that enters into ones mouth and nose

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, sallallaahu 'alayhi wa sallam, is His slave and Messenger.

Purifying the inside of the mouth or nose from impurity is no different from purifying impurity from any other part of the body.

Purification is done by pouring pure water into the mouth or nose until one predominantly believes that impurity is removed to the extent that no trace of it remains, such as its taste, smell, or color.

However, being certain that it became pure is not a condition for purity (predominantly believing that it became pure is sufficient).

Al-Mubdi’ Sharh Al-Muqni’, which is a Hanbali book, reads: “What is meant by abundantly pouring water on the impurity, is until it submerges it in a way that its color and smell are removed; if they are not removed, it is not purified.” [End of quote]

Additionally, Ar-Rawdh Al-Murbi’ with its footnote reads: “It is sufficient to predominantly think that it has become pure; (i.e., for the impurity to be removed).”

Allah knows best.