The nasty habit of a puppy eating their own stool is very common.  There’s even a name for it:  Caprophagia.  It is very unlikely a health concern.  Here is an article that goes over the topic in quite a bit more detail: https://www.vetbabble.com/dogs/questions-dogs/why-does-dog-eat-poop/

In some cases, it can mean that they have worms or a nutritional deficiency.  The best way to ensure none of these things are going on is by visiting the veterinarian and ensuring your puppy is current on all their preventatives and that they are happy and healthy.  However, it is likely behavioral and may need some modifications.  It could be a passing stage, but oftentimes it continues into adulthood if they are not trained out of the habit.  I definitely encourage you to read the article though and maybe start working on some behavior modifications to help remedy the problem so long as your puppy is declared healthy by a veterinarian.