I Am Having Bloody Nose For No Apparent Reason. It

I am having bloody nose for no apparent reason. It last for at least 30 minutes. I had a nose bleed earlier this afternoon and now. When it bleeds it runs down the back of my throat as well out of my nose. The color is bright red. When it clots usually I have to spit out the clot then it will stop. I don't understand why this happens. Should I be concerned?