Topping up with formula milk

Hi, just gave birth last week. Noticed my pedia is so keen for me to breastfeed and lactation consultant, but it has been stressing me out. Last checkup with pedia she didn’t suggest formula milk as baby is not dehydrated. But my nipples are already bleeding and not feeling well. Do I have to ask permission from pedia for topping up with formula milk or just go with it? Cause i feel like they won’t allow me