Would appreciate an answer to whether I'm being anxious for no reason or for a reason hehe 

Priority seats are reserved for people with mobility issues.

I don't know the policy of Trenitalia on this subject, but on most carriers it's okay to sit there when there's nobody who needs that specific seat. 

But if someone without a mobility issue has booked the seat, then a person with a mobility issue can't book the seat.

@BrendanDB thanks. Unfortunately i didn't know what it was during booking, as it was not specified. Is there a way to change the reservation? Or will this create issues during journey time