Nose blocked after rhinoplasty. What would be the solution for this?

There are many causes of nasal obstruction being caused by Rhinoplasty, and without examining your nose, no surgeon can assess your problem and it's solution.
The simple answer is - when Rhinoplasty makes a nose smaller on the outside, it also make it smaller on the inside.Rhinoplasty can also cause weakening of the nostril cartilages, causing "valving", it can cause internal scarring, it can change the direction of airflow causing turbulence.
There is not much difference between Plastic surgeons and ENT surgeons in how they do Rhinoplasty, (some from each specialty do them well, some do them poorly), but there is a significant difference in what most ENT surgeons do on the inside.I suggest you consult with an ENT surgeon with experience in rhinoplasty to try to solve your problem.