This article explains how to delete Instagram posts. The instructions apply to Instagram.com and the Instagram app for iOS and Android.
How to delete Instagram posts
Technically, it's not possible to delete individual posts on Instagram, but you can delete entire conversations.
To delete chat conversations in the Instagram app, go to your messages, tap and hold on a conversation (on Android) or tap and drag a conversation to the left (iOS), then tap Delete.
Open the conversation on Instagram.com, select the Information icon (i), then select Delete Chat.