What if I can barely feel my baby's soft spot?

Some babies have a smaller or less noticeable soft spot, especially at the back of the head. If your pediatrician hasn't raised any concerns at checkups, a faint soft spot on its own isn't a worry.

Can a toddler hurt the baby's soft spot?

Gentle touching or patting won't cause harm. A toddler hitting, poking hard, or dropping something on the baby's head is a different matter, so keep an eye on play between siblings, as you would anyway with a young baby.

Does vitamin D affect when the soft spot closes?

It can. Rickets, a bone condition usually caused by low vitamin D, is one of the known causes of a soft spot that stays open too long. The American Academy of Pediatrics recommends a daily vitamin D supplement of 400 IU for breastfed and partly breastfed babies, so ask your pediatrician whether your baby needs one.