Thanks for stopping by the Apple Support Communities. I see that you've recently updated to iOS 12.0.1, and now you see a badge app icon on your Settings app, indicating there is one notification. I'm happy to help!
While the badge app icon does appear when an iOS update is available, it may appear in other instances. For example, you may need to enter your Apple ID password for iCloud and/or other Apple services like the iTunes & App Store, or there might be an update for your wireless carrier ( Update your carrier settings on your iPhone or iPad - Apple Support ). I recommend selecting the Settings app to see what the notification is related to.
If it is indicating there is an iOS update, force close the Settings app: How to force an app to close on your iPhone, iPad, or iPod touch - Apple Support , then restart your iPhone: Restart your iPhone, iPad, or iPod touch - Apple Support .
If you still need help, don't hesitate to respond back.
Cheers!