Praise be to Allah.
The Prophet’s Sunnah indicates that the nose may lead to the stomach. The Prophet (blessings and peace of Allah be upon him) said: “Exaggerate in rinsing the nose (when doing wudoo’) unless you are fasting.” Narrated by Abu Dawood, 142; at-Tirmidhi, 788. Classed as saheeh by Shaykh al-Albaani in Saheeh Sunan Abi Dawood.
If the gel that is taken through the nose does not reach the throat or stomach, rather it is absorbed through the nose, then the fast is valid.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
There is nothing wrong with using creams that moisten the lips and nose, or dampening it with water or with a wet cloth and the like, but you should take care not to let any of that moisture reach the throat or stomach. If anything does reach it without you intending it to, then you do not have to do anything, such as if you wash inside your mouth and the water reaches the throat without you intending it to. That does not break the fast.
End quote from Majmoo‘ Fataawa Ibn ‘Uthaymeen, 19/224
We ask Allah to heals you and all the sick Muslims, and grant you well-being.
And Allah knows best.