If you see a post or profile that’s not following Instagram’s Community Guidelines (ex: nudity, spam, self-harm), you can report it.
To report a post:

1. Tap ••• (iOS and Windows Phone) or  (Android) above or below the post
2. Tap Report 
3. Tap It’s inappropriate
4. Follow the on-screen instructions

To report a profile:

1. Tap ••• (iOS and Windows Phone) or  (Android) in the top right of the profile
2. Tap Report (iOS and Android) or Report for Spam (Windows Phone) and select It’s Inappropriate
3. Follow the on-screen instructions

Learn how to report a comment.
When you report something, your information isn’t shared with the person whose post or profile you’re reporting. Keep in mind that the number of times something is reported doesn’t affect whether it’s removed from Instagram.
If you don’t have an Instagram account, you can report someone using this form. If you’re trying to report a post or profile you can’t see, ask a friend who can see the content to report it.