What is the treatment for deviated nasal septum (DNS)?

What you describe appears to be due to a deviation (shift) of the nasal septum (the central partition that divides the nose internally into two). This would naturally result in narrowing of the internal nose on one side resulting in nasal blockage. Such a condition is best treated by an operation called a septoplasty, where the surgeon frees and straightens the septum, thus improving the nasal airway. Medication has little role to play unless there is superadded infection or allergy. Septoplasty surgery is very effective in the appropriate setting and the cost would depend on the individual surgeon, the nature of anaesthesia (local or general) and the hospital where it is carried out.