First, have someone else shoot it to make sure the gun is at fault, not you.
Second, if the gun does need work, examine the sight and determine the best way to file it to keep a good looking profile. (Important if you sell the gun.)
Third, if possible, take the gun and a file to the range and file as you fire. Stop a bit shy of zero so you can finish the job at home where you can keep the right profile and angles.
Jim