Fever?

My baby boy got his vaccines today and we also took him to do some blood work because his pediatrician wants us to see if he might have something...I plan on doing an update on this once it’s all official. But he is currently sleeping on my bed I was about to move him to his crib where he normally sleeps and I felt him hot so I decided to check his temperature and it was 100.3...is that a fever? I heard 103 and up is a fever but I some people say 100 and up. I plan on checking it again just in case it was him being covered and being to hot but please I don’t know if it’s a fever or not. I have Tylenol on hand.