No one is so interesting that they can carry a story by themselves.
You may love your character, but you're asking a lot if you want readers to stay with them for an entire novel without anyone else around or any extraordinary circumstances.
In some cases, nature might become your second character. You might have characters outside the scene that the main character remembers or talks to in his or her mind. You might have the weather be its own character to antagonize a character who's stuck on a boat.
Whatever you're writing, remember that it needs to interest readers, and that few readers will be interested by just one character.
Make sure that you give readers something equivalent to another character to cling on to and love or hate as you write.