When I am sick it always becomes hard for me to do wudu because I can’t inhale the water I put in my nose and when I blow the water out, my nose starts leaking. What should I do?
Allah azzawajjal said Allah does not obligate anyone beyond his capacity.(2:286)
It is reported by our beloved prophet Muhammad PBUH,
on the authority of Abu Hurayra(RA) who said : I heard the Messenger of Allah say : What I have forbidden for you, avoid. What I have ordered you [to do], do as much of it as you can.(bukhari and Muslim)
There are two options you can follow once faced with such a situation, one is dry ablution (tayyammam) for the nose and the other is to try to wash/rinse as much as you can.
Sniffing/inhaling water is not necessarily a requirement in such a scenario as the nose can be washed without actual sniffing. When a person is experienced a blockage, he can insert water into the noise either by blowing his nose then sniffing in water, or tilting his head back to insert water, or inserting the fingers in the nostril to guide the water around the nose.
So keep your duty to Allah and fear Him as much as you can (64:16)
Ref : Zaad al-Mustaqni and Fataawa Arkaan al-Islam by Shaykh Ibn ‘Uthaymeen.
May Allah the mighty and sublime grant us mercy and guide us to the straight path.
Allah knows best