When you change the URL of a blogspot blog, the permalink (individual post URL) also changes and if the blog already has incoming backlinks, these links will become dead links (page not found). So if you are unhappy about that, what can you do?
I would suggest going back to Blogger dashboard, click SETTINGS then PUBLISHING and change the blog URL back to the original blog URL. Of course you will need to do it fast because that option will not be available any more if another blogger has already registered that URL. If successful, all your original permalinks will be restored.
I have tested it at a test blog Computer Hardware Tips and Tricks and confirmed that after changing the blog URL back to the original, the permalink of the individual post had also been restored.
More details - original permalinks
and when changed to a new blog URL, these permalinks became (those changed items in red)
and when the blog URL revert back to its original URL, these permalinks then become changed back to the original as shown below: