It's very possible that there was some trash/debris floating around in the fuel tank and when the engine ran out the stuff was sucked into the fuel line.
If you're sure the fuel lines are clean and debris free, you'll need to remove the bowl of the carburetor to clean it out. It's possible to have some trash/debris sitting in the bottom of the carb bowl that it stopping up the jets.
Normally in these circumstances it is fuel related problems causing trouble. It's also possible that you over primed or over choked when trying to re-start and flooded the engine. Take the spark plug out and see if it's wet. If it is, dry the plug off good and let it sit with the plug out for about an hour. Put the spark plug back in and see if you can start the mower.