It just made a little fire, it didn't "explode". It would melt your floppy drive and make it useless but wouldn't come close to doing enough damage to hurt anyone unless they had their face a few inches from the front of the PC.
Unless the strike surface also contained an accelerant, as well as the igniter...:)
I'm guessing that there are plenty of things that would fit in the floppy and cause serious damage. Mercury fulminate maybe, or ammonium triiodide(?), assuming they didn't just self-detonate.