I am having this problem for more than a year. Most of the time, one side of my nose is always blocked. This happens mostly on the right side. I don't have flu and both sides of my nose are dry. The only difference I can see inside the right side, there is a bump which I think is limiting the air entering and it changes side of the nose. Sometimes I need to breath by mouth and that give me headache. Anyone know what is causing this?

Have you been to a doctor in the last year to ask them? They will have a far better answer than someone on the internet that can't examine you.

You need to check with the doctor, to be sure that there is not a growth, that may be blocking the airway.

Finding out the reason, will then determine what is the best course of action.