puppies don't usually start eating puppy food until around 8 weeks. that's when most people wean them off of their mother
8 weeks is very incorrect! I raise Chihuahuas and I start my puppies on canned food at 3 weeks. If not, they will start trying to eat the mothers dry food around that time. At 4 weeks my puppies are usually helping themselves to the dry food. There should be dry food with them and available to them at all times. Try some good puppy canned food, I would be willing to bet your puppy will dig into it. Feed it away from the mother or the mother will try to eat it all before the puppy can. Some mothers will even growl at the babies for trying to eat from her bowl.
I, too, start puppies eating gruel made from the hard kibble blended with warm water at 3 weeks. While momma is out going potty, babies eat their fill of it. Then momma comes back and finishes it, and cleans the babies as they can make a considerable mess, falling headfirst into the platter, stepping in it, etc. By 4 weeks old they have their heads in the food bowl but ususally don't get good enough teeth to crack the kibble until about 5 weeks old. As soon as I see them eating hard food, I stop the soft food. Mommas usually start weaning around 6 weeks, certainly by 7 weeks, and puppies have been eating entirely on their own for over a week before they go to new homes at 8 weeks.