Did the baby cry when she did it or did she scratch or cut it? If not, I wouldn't worry, although it's called a "soft spot" (clinical name:fontenelle), its actually not so soft. It's covered by a thick fibrous membrane. It would take a lot more than a poke from a 2 year old to penetrate it.
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Warmly,
Chase
#1 Just Answer Parenting Expert
Just Answer Parenting Mentor, Emotional, Behavioral & Physical Issues. Babies to Teens.