If I need to make an obligatory ghusl, and have a blocked nose, and hence water cannot reach the upper part of my nose, what do I do to make my ghusl valid?
We do not understand what you mean by blocked nose.
If you mean having a cold, that does not stop the water from going up.
However, in Ghusl, it is sufficient that the water reaches till the soft
portion of the nose.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai