Where Are The iOS Updates Stored On iPhone?

I downloaded iOS 9 on my iPhone 6 and I decided to install it the next day. But, the very next day iOS 9.0.1 was launched and i was not able to install iOS 9. It also disappeared for General>Usage and hence, it is utilizing storage on my iPhone but can't be installed. Can anyone tell me how can i delete the iOS 9 update?

Once the new one comes out you can't get the other one. So you have to download the 9.1

Installing the latest should clear out any lingering updates, if not backup, then restore, restore from that backup to see if that helps.