Can I travel to Nigeria on expired Nigerian passport?
A visa is required.
However, no visa is required for current/former nationals of Nigeria with a valid foreign passport and an expired Nigerian passport.
Caveat emptor: This information should be double checked for accuracy. Seek the experience of people who have traveled to Nigeria under such circumstances.
The main challenge from what I found out are the airlines. An airline may not allow you to board without a visa. So before you take any decisions about traveling to Nigeria on expired Nigerian passport, contact the airline first. Obviously, if you're not traveling on a direct flight, you must call multiple airlines.
Of course, immigration officers in Nigeria could decide to flex some muscle. But ultimately, you can't be denied entry into your own country. The video below is a good reference.
Here is a more recent video on the same topic...
Just as it is with anything involving Nigeria, buyer beware. What the law says is one thing. But always have a plan B, in case things do not go as it should. Hope for the best, prepare for the worst.