Oh, the poor little thing. That had to hurt.
It's most likely a double yolker or even a rare triple. Any pullet or hen can lay a weird egg every once in a while, especially at the beginning or end of the season. Pullets seem to be especially prone to it because their bodies are still growing and getting everything in sync.
The occasional double yolker is normal but not commonplace. I had a little Easter Egger pullet crank out a double yolker this spring, followed by a tiny egg with no yolk at all. Her body's timing was just off. She finished that laying cycle, took a few days to rest, and started her next cycle with no problems at all. She hasn't laid another weird egg since.
Because your pullet broke a blood vessel while laying this egg, it's a good idea to check her vent for signs of bleeding or prolapse. If you see any blood, and especially if anything pink, gray, or red is hanging out, wash the area with warm soapy water, and poke back in anything that's on the outside that shouldn't be. If there's bleeding or prolapse, you'll want to isolate her from the flock for a few days until she recovers. Not quarantine, just put a fence between her and the others so they don't pick at her and make the problem worse. Chickens instinctively peck at what's red or bleeding. They don't mean to be cruel, but "red = tasty" is how their minds work.