Keep doing it for a month twice a day.
The trick here is to learn to do it with your mind whenever you realise you are stuck in ida or pingala ( left & right nostril reaspectively) balnce will come over time and the two brain hemispheres will re-balance. They will actually start talking to each other more because one will not play the dominant role and the other dormant or latentt. Intelligence and creativity will increase dramatically ,as well as health.
So if your ida is dominant ,your left, then bring just a little more focus to pingala, the right nostril, and over time the neurological circuitry will reconfigure itself to more optimal and healthier level of functioning. Also energetically , your subtle nervous system,you will have more energy and feel more balanced.
It really does work. It is just a matter of re-training. Like anything in life if you work patiently on it-revising for exams ,working out at the gym ,starting up a business etc.
Eventually the more blocked nostril will open ina few months or less. It could have been this way for decades, & years and years. All you are doing is re-training your nervous system and some of the underlying physiological and seemingly autonomic processes that govern it. This is why pranayam is so powerful and more deserving of being taught.Nadi shodhan is one of the kings of pranayama i think.It is a real key. Just like sirsasana is to asana for instance. A bit like that.