Formula Shelf life

I just a comment on a tik tok saying formula is only good after a month of being opened and now I’m worried because I have been giving my baby the same formula for over a month. He only takes 2 teaspoons a day from it because it’s used to fortify his breastmilk. I wasn’t told this information and I checked what the can says and it says to use by date on can which says use by January 2024 but that probably means unopened. Do I have to go buy a new one??

It was given to me by the nicu so i’m not sure when it was opened