Your best course of action would be to take him to a vet. The staff on this forum can tell you what it appears to be, but only a vet can diagnose and treat illness. From the stripes on the head, it looks like a young bird. Those stripes fade as they molt and get older.
What is your baby's name? Where did you get him from? Does he have other cage mates? If you haven't done so already, it's extremely important to take your new friend for an initial well birdy check up! Birds in the wild, being a prey animal, will hide illness (and injuries) to prevent being taken by a predator. Like us humans, all living beings want a quick easy meal, and a prey animal thats weak fro illness or injury gives a predator the perfect opportunity. By the time a budgie starts to show signs of illness they have been sick for quite some time. Ideally an avian vet would be your best choice, or a vet with experience with exotic animals. It's awesome by the way, that you are being vigilant about observing your sweet, adorable baby 😊!
What is your baby's name? Where did you get him from? Does he have other cage mates? If you haven't done so already, it's extremely important to take your new friend for an initial well birdy check up! Birds in the wild, being a prey animal, will hide illness (and injuries) to prevent being taken by a predator. Like us humans, all living beings want a quick easy meal, and a prey animal thats weak fro illness or injury gives a predator the perfect opportunity. By the time a budgie starts to show signs of illness they have been sick for quite some time. Ideally an avian vet would be your best choice, or a vet with experience with exotic animals. It's awesome by the way, that you are being vigilant about observing your sweet, adorable baby 😊!