Advice/Don’t know what to do

Hi so just found out at around 10pm that my baby boy’s temperature was 100.5. I gave him Infant Tylenol, I didn’t know if I should’ve or not. His temp went down some 99.8 but checked again when he woke up. It went back up to 100.4 ( right now it’s 2:40am, i checked at the beginning of 2am) I don’t know exactly what I asking, but I’m at a loss trying to figure out what to do exactly. My LO is 4 months old. Update: Went to the ER with baby boy and got prescribed tylenol (children’s). he got diagnosed with Covid 😣 Pretty much just have to monitor him, give him medicine every 4-6hrs and quarantine.