OK! No worries - as you say, this error is appearing because you deleted your first post, and, at Settings > Reading in your dashboard you've got your front page set to display your most recent posts. So, as there is nothing to display, you're seeing this error message.
To fix this you can do one of two things: publish another post which will therefore appear in the place of this error, (you can publish a post from Posts > Add New in your dashboard), or you can go to Settings > Reading in your dashboard and change the front page setting to display one of your static pages instead of your most recent posts (static pages can be created from Pages > Add New in your dashboard).