Thank you for your query
I don't think you need to worry a lot about this. Minor asymmetry in a child head's structure is not a problem. It can be due to difficult labour, some hematoma
which was present earlier and now has calcified. It may also be a mild bony overgrowth which is not much of a problem. Things tend to settle down or become less prominent as the child grows. Only worrisome thing can be abnormal fusion of a child's skull bones called craniosynostosis
. Since a pediatrician
has seen your child it seems unlikely. However you can take the opinion of a pediatric surgeon as well.
Hope that helps
God bless you