You’re talking about a bridge, not sure if anyone has created one for instagram yet.
I think there is a bridge to the fediverse, if there is a bridge from instagram to the fediverse, then theoretically you should be able to bridge from your instagram, to the fediverse and then here.
Thinking about it, that may be more work than it’s worth, you may be better off just waiting til a developer creates one from Nostr to instagram.😅