I can't say what you saw, but it certainly wasn't a star exploding. Naked eye supernovae are extremely rare events (one every several hundred years). Their brightness ramps up over the course of hours, but even then their apparent size would be pointlike. It takes decades for their ejecta to appear as an extended object to our most powerful telescopes, and you'd never see it as an extended object with your naked eye.
So what could it have been? It must have been in the atmosphere, or just outside of it. Perhaps it was a meteor coming directly at you. That's a highly unlikely event, but it must happen to some people.
Further questions: what year was it? How bright was it compared to the stars? Or compared to the full moon? Was it any particular color? In what part of the sky did it occur? When you say that the light rushed away in all directions, did it come out as a solid circle, or as an empty ring or sphere, or did it shoot rays outwards, like spokes? Finally, how big did the distribution of light get before it faded?
It was white, the same intensity as the stars around it, No color at all. The light spoked out evenly, but appeared no bigger than a pea. It happened very rapidly and left no visible trace in the air. It was somewhere around 1979, looking directly upward near Mammoth Lakes, California. It wasn't moving across the sky, but straight at us is a possibility. Thanks for the input.