What is the ruling on dried nasal mucus in the nose, and does it act as a barrier to ablution, according to the opinion that sniffing water into the nose (istingshaq) is obligatory?

The obligation in istinshāq (sniffing water into the nose) is to draw water with the breath and introduce it into the nose. It is not obligatory for the water to reach all parts of the nose. What was mentioned does not affect the validity of the ablution.