How should I fill a hole in a basement floor where there is dirt underneath?

Our basement floor has an approximately 4 inch diameter hole, pretty close to the drainpipe. As far as I can tell, the hole is where there was some kind of bubble in the concrete and the top broke open. The amount of area that I would need to fill is about the size of a coffee mug. Never done any concrete repair before - what do I do? I mostly just want to be able to wash the floor without stuff going into the hole, so it doesn't have to look great.