I just tried to use a tampon for the 1st time & when I put it in, I started to drip blood. Only lasted few seconds, no pain and very light. But I'm worried I broke my hymen. When I removed it there was a flat blood clot on it and I'm just worried?

First of all, that's not how the hymen works. Hymens aren't like "fresh and seal" wraps that are in your vaginas and they do not break. Yes they can tear but you can like puncture a hole in it or anything like that. Many of the things that people tell you about the hymen are not true so don't worry, you didn't break anything. 

Now about your tampon. The blood and the clotting is all from your menstrual blood and it's normal! For someone who isn't experienced in using a tampon yet or even during heavy flows, it's totally fine for there to be some leakage. And the clotting on your tampon simply indicates that your tampon is working. You also said that you didn't experience any pain or very little which is good. Pain and discomfort are usually a bad sign that you either inserted it wrong or your vaginal canal is irritated by the cotton or the scent from the tampon. But since you didn't experience any of that, I wouldn't be too worried.