How did you fill it? Did you use the Paint Bucket tool?
Most of the time it's better to connect the nodes. That way you can use the traditional fill. The Paint Bucket tool takes a lot more time to tweak and fidget with, than connecting the nodes.
It is possible to get a nice fill with Paint Bucket, but as I said, it takes a lot more time fussing with the Node tool, to get it right. For me, it's much faster to just connect the nodes.
But it depends on the kind of work you're doing. There are times when Paint Bucket tool works fairly well.