How to skip iOS 9.3 update?
Option 1: Delete the update from your iOS device.


Go to Settings from your Home screen
Select Storage and iCloud Usage
Go to "Manage Storage"
Find the iOS update that is bothering you and select it
Tap on "Delete Update" and confirm


However, you'll have to stay off of Wi-fi, otherwise it'll re-download.

Option 2: Block Software Update domains on your router / gateway

You'll have to figure this one out on your own, since all routers are different, but the domains you'll want to block are:


appldnld.apple.com
mesu.apple.com


Option 3: Just update

You can also give in and submit to the installation. This will bring you up to the latest, most reliable and up-to-date version of iOS, but if you don't want to, that's definitely fine.