You don't need to delete it, it's no big deal - duplicates of all sorts happen all the time and if they end up somewhere they shouldn't be, users and/or moderators sort it out.
You could also repost somewhat earlier if there's major rework/features, etc - the point of this stuff is not to discourage people from showing their own work, just to avoid excessive samey-ness.
You could also repost somewhat earlier if there's major rework/features, etc - the point of this stuff is not to discourage people from showing their own work, just to avoid excessive samey-ness.