It is not good. It can mean the puppy has serious intestinal infection (dysentery) or is constipated and straining to poop. Either way, you should take it to the Vet.
What Does It Mean When My 2 Week Old Puppy Is Bleeding From Her Butt?
It means to see if the vet can fit you in today. That is nowhere near normal and a BIG concern. Internal injury, parvo, severe bacterial infection, a lot of things and they can't handle much at that age. I hope you can fix whatever it is and good luck.
She could have parvo take her to the vet ASAP