ANY white spots on the iris or pupil in general need to be checked out. There are many diseases of the entire body that present with eye issues or eye abnormalities as one of the symptoms. Goldenhar Syndrome is one of them, as is retinoblastoma, a type of cancer. You should always ask for a second opinion and seek the advice of a pediatric opthamologist.
Goldenhar Syndrome discolorations look like this:
http://dermatlas.med.jhmi.edu/derm/IndexDi
splay.cfm?ImageID=476091055
*I would like to point out that Goldenhar Syndrome is a rare syndrome and that your child most likely does not have it, especially if s/he does not present with the other symptoms, however, it, as well as many other conditions is a prevalant reason why you should get your child's eyes checked if there seems to be a problem.