Will I blow my ballast?

[UnoZeus]

I think I blew my ballast on my T5 fixture, but I am a bit confused.

I have a 4 bulb fixture. When I turned the fixture on I heard a pop. One of my bulbs didn't work anymore. I figured I blew the bulb so I tried another. Not the case. So, I figure I blew the ballast?

If I continue to run the existing 3 bulbs, will that make matters worse? Or should I continue to use atleast 3 until I can replace the ballast?

Thanks in advance!