How can I install a regular light fixture where a ceiling fan used to be?
You probably should have paid more attention to what was connected to what. In all likelihood, the "sw" bundle has a wire that was carrying hot (power) from the unswitched wire at the fixture to the light switch, and the other wire was returning that power from the switch. The switched wire should be but often is not re-colored red in that application (ie, a back/white/ground cable running to a switch should have red tape or paint on the white wire ends if it's a "switched hot" rather than a neutral.)

That does not meet current code (which requires a neutral wire at the switch) but met older codes and was very common (a switch loop.) 

As such, the expected configuration that will probably work if things are wired normally would be cable blacks together, white from unswitched cable to white on fixture, white (recolored red for clarity) from switched cable to black on fixture, and grounds all together.