Can still feel a skull suture on one side of 5 yr olds head

[PJ67]

I was rubbing my son's head last night and felt a little indented area on the right side of his head. After feeling his head more it seems to be the Sagittal suture on the right hand side and feels like a little ridge. Is this normal and why would I only feel it on one side?
Thanks

Oops, just looked it up and it must be the coronal suture as the Sagittal one runs along the middle!