All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
This mucus that comes out of one’s nose is pure, and it is not an obligation to wash it off; nevertheless, it is only permissible to wash it off to remove the dirt. Also, if a little bit of mucus is mixed with water, it does not affect its purity.
Moreover, if the water flows on one’s face while there is some mucus and this mucus does not prevent water from reaching the skin of one’s face, then the ablution is still valid.
Allaah knows best.