"On the run detail screen, tap the "Settings" icon in the upper right-hand corner.
Tap "Edit Run."
Tap the Date, Distance, Duration, or Pace field to edit.
If you select Distance and Pace only, Duration will be calculated automatically; if you select Distance and Duration only, Pace will be calculated automatically.
Tap "Done."
Review your edits on the run detail screen and the Activity view.
Note: Not all runs can be edited.
Only runs you have recorded on the Nike+ Running App can be edited.
If you log out of the Nike+ Running App, or delete and reinstall the app, your past runs will no longer be editable."
https://www.youtube.com/watch?v=seVdI6FGjk0