Not sure which one applies.
- Open the Nike+ Running App.
- Tap the Menu icon in the upper left-hand corner.
- Tap "Activity."
- Locate the workout you'd like to delete and swipe it right to left.
- You should now see a "Delete" button on the right side of the activity. Tap "Delete" to remove the workout
OR
- Open the Nike+ Running App.
- Tap the Menu icon in the upper left-hand corner.
- Tap "Activity."
- Locate the workout you'd like to delete and press and hold.
- You should now see a window pop up with the option to "Delete Run". Tap "Delete Run" to remove the workout.
I am not sure which one works but I am VERY sure one will solve your problem