Birds do not realize the strength of their beaks on skin, so like small children, they must be taught limitations as to what is acceptable and what is not. Similarly, young birds likely will not realize that new foods are food, unless they have been taught so, by their parents, siblings or other flock members. This is why you will find many postings suggesting you, the young bird's new flock eat/taste new foods in front of and with the bird(s) while making enthusiastic sounds. The same holds true for toys.....birds are not hatched knowing a ball or bell can be fun to play with, they have to be taught.....
Good luck.....