Are there any procedure to widen the nostril so as to improve breathing. Due to deviated septum my one nostril is blocked.

If the nostril is blocked by the septum, a septoplasty (with or without rhinoplasty) may be all you need to improve the airflow. Some deviations, such as at the caudal end (the leading edge of the septum) require additional techniques like a caudal end strut graft to maintain support of the nose. A detailed exam can usually reveal whether the problem is just the septum or a combination of septum, nasal valve area, inferior turbinates, various nasal masses, etc. Note that none of this actually requires widening the nostrils.Hope this helps,--DCPPearson Facial Plastic Surgery®

Hi,
If the blockage of the airway is due to the septum, then a septoplasty will address this. Regards enlarging the nostril though, this is difficicult, but if the objective is a free passage of air flow then the septum is likely the solution.
Jeremy Hunt

Thank you for your question.  Many rhinoplasties are, in fact, performed for improvement in function (breathing) not just for appearance.   Without pictures - or better yet an exam - it is difficult to say if your nose would be amenable to such treatments.  Sometimes the septum itself can be treated with good relief of symptoms.  Others require a more involved procedure such as rhinoplasty with internal cartilage grafts to improve nasal airflow.  It would be best to seek out a board certified surgeon with experience to help you understand your options. Best of luck!