It’s absolutely OK to make an open-source project that may have no users other that yourself. You have at least one user, and you know exactly what features that user needs and which bugs are the first priority for that user.
It’s much harder when you do something for an “average user” that may not even exits. You exits, at least, and that’s a good start.
I have at least one open-source project that I know for sure no one but me has any use for. But then again, I have at least 3 open-source project that I was sure would fall into the same category at the time I was developing them but that turned out to be of use for at least one person other than myself each.