TMI period question!

This happens sometimes while I'll on my period, and I'm wondering why this is, and if it's something to be concerned about.

So I just went to the bathroom. I removed the tampon and it wasn't even entirely full. Then I wiped and there was a huge glob of thick blood. It looks like I just scooped up a spoon full of jam (totally gross, I'm sorry).

So there's just this 2-3inch diameter glob of blood just sitting there on top of my tampon and not getting absorbed.