Could my LO be sick?

We literally don’t take our LO out since it’s so nasty with the snow and such. He’s been just fine this whole time and then all of a sudden tonight his nose started running a little bit. He also sneezed a few times (which I know is normal) but a little snot ran down afterwards. The hubby and I are both well so I don’t know how he could get sick. No ones been visiting so that couldn’t be it. I have been feeding him breast milk from the fridge all day today since it was about to go bad, could it be that? Or is it just random sickness?