According to the official Apple changelog, iOS 9.3.1 fixes an issue that caused apps to be unresponsive after tapping on links in Safari and other apps. Since this is a level 3 (very minor) update, there is no urgent need to upgrade. Users experiencing bugs and issues with Safari are encouraged to update as soon as possible
Below are the direct download links for iOS 9.3.1 IPSW files used to update and restore your device via iTunes. A full list of previous releases is available on our resource page.
Be sure to check out and bookmark our resource page which contains links to all iOS versions.
Jailbreakers please see this page to see if a jailbreak is available.