Why does this message keep popping up?

I started using my other iPhone because the one I had got stolen but this is the iPhone that I downloaded IOS 9 beta on so every time I turn on my phone, this message that says to update to IOS 9.1 from beta keeps popping up. So I checked the software update place to update but it says IIm up to date? I would just ignore it but now it's starting to get annoying. Please help, how do I get rid of it or update to iOS 9.1?

Couldn't find instructions for IOS 9. See if this helps:

http://www.imore.com/...se-version