I've had this problem for a while and its not consistent. I'm 16 and i have recently realized this sensation. I barely get sleep and one of the causes is due to this. There is a flap like sensation in my right nostril. I used to have horrendous nose bleeds from my left nostril which would cause there to be blood clots coming out of it. I also used to have (for a short duration) CSF leak. The right nostril has not unblocked, i have tried nasal sprays and nothing has changed.