Yes. If you have 1 file then you are using 1 inode (well, there's also a couple of extra inodes used by default for other purposes just because of the way the filesystem works; e.g. the base directory and
lost+found need inodes).
The other inodes are wasted... but they don't necessarily use that much space. You may be able to gain a few Mbyte...
When you make a filesystem you should consider what type of usage you're going to put on there. If it's a lot of small files then you might want to increase the number of inodes. If it's a small number of large files then you might want to decrease the number of inodes. This can be specified, for example, with the