That’s very much possible, other things that happens to kitten, is that they sometimes get hurt unknowingly, especially when other kittens are around . And mother cat may press too much on the belly area of kitten while they move their kitten ., but I want to know whether it is Vomiting or regurgitation. Regurgitation happens to kitten which are on milk or some liquid or semi solid diet . Regurgitation can be cured by keeping the head on some raised surface after feeding and also by reducing the quantity of feed by half .

There are multiple causes that can cause vomiting. A few of these causes may be indigestion, food allergy, parasites or infections. So, visit a vet or start a consultation with thorough history and diagnosis, root cause may be identified and treated thereby.

Vomiting can happen due to so many reasons. It can be due to indigestion, infection, toxicity, hairball, or foreign bodies, disorders, etc. In your case, the kitten is so small that he may have indigestion or infection. Medicine will help him so kindly get veterinary help for him.