Hard core Instagram users, you will not be able to share photos into Instagram without opening the app. The latest version 8.2 allows you to share both photos and videos from Photos or other iOS apps directly. This is done by a new iOS extension that you can access once you update the Instagram app, simply open an app like Photo to see the new extension for iOS.
Third party app extensions have been possible since iOS 8 was introduced in 2014, and an official Instagram share extension has been widely requested since then. Prior to iOS 8, Apple offered integration with Facebook, Twitter, Flickr, and Vimeo, but other third-party apps weren’t built in to the share sheet. – Source: 9to5Mac
However if you like to use filters and other editing features, you will still need to launch the full app. So this is more for images that you already like to upload to the platform.
Check it out.