If it's still not working, try uninstalling and reinstalling the app.
Instagram is the world's most popular app for sharing photos and videos of your life, but since yesterday, June 4, there's been a bug that's caused the Android app to repeatedly crash. The issue was affecting Android phones of all kinds, but thankfully, the issue's been fixed.
According to a Tweet that Instagram shared this morning:
Yesterday, there was an issue causing the Instagram app to crash on Android devices. We're sorry, and things are resolved! If you're still experiencing problems, try reinstalling or updating your app.
The app appears to be working fine on my end, but as Instagram notes in the above message, uninstalling and reinstalling the app should completely eliminate any crashes if you're still experiencing them.