How to use Nike Running with iOS 8's Health app?
Nike (and all the others providing similar things) needs to update their application to make use of HealthKit and send data to the Health app.

Apple has announced that these updates also will not be available until later in September 2014:


http://www.loopinsight.com/2014/09/18/apple-pulls-healthkit-apps-after-discovering-last-minute-bug/