My 40 days old labrador puppy had vomiting and now its not eating anything. Please suggest sumthing?

You should see your vet today and the only thing that can be done. Those symptoms could indicate many things but when they are just starting out life they can't handle much and even more easily corrected things can take a turn for the worse and mean life and death very quickly.
Those symptoms would be a concern in even a more stable older dog but they are very fragile while that young. Parvo would also be a particular concern in a pup who has not finished their puppy sets yet.
They can indicate things like bacterial or viral infection like parvo, poisoning or blockage as a few possibilities.
There is also a concern that it may be something that could run through your entire litter or may be something like a nasty bacterial infection that was passed from the Dam since they are usually still in the weaning process at that age and may be a concern for her as well.
See your vet. They will have a better idea of what may be going on once they are able to examine your pup and talk to you about everything. Once they know what it may be they will know what can be done for your pup. I hope your baby is feeling better soon. Good Luck.
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Bring it to the vet. It could have ingested something blocking it's intestines, like a coin. This could be lethal if not treated. Also, what are you feeding it, it seems early for it be away from it's mom and not drinking milk.