Advice please!

Brienna
Hello all, my 4 month old son got shots today at 11am it's now 12:30am so about 13 hours later, and I just left for work of course and husband is home with him but says he's really hot, temp was 100.8, and very fussy and inconsolable. I know they sometimes can have reactions to shots so when do we know to do something and bring him to the hospital? I told him to put a cold face cloth on him and take his clothes off and he gave him some Tylenol. And it seems to have calmed him but still wondering when and if would be a good time to go to the hospital because of something like this. Thanks in advance!