A hatchling is a baby bird that's just hatched from an egg. Any other animal that hatches from an egg is also a hatchling. Since you are human, you are NOT a hatchling.
While hatchling is most often used for a young bird, newly-born turtles, tadpoles, and newts are all hatchlings too. Sometimes people find bird hatchlings in distress and nurse them back to health. Occasionally, these hatchlings seem to see their human caregivers as parents. Hatchling uses the diminutive -ling suffix, like the words gosling or duckling.