Things to look out for would be a red inflamed throat, fussy and crying. He may reduce his feeding and he may develop a fever. He may develop rapid breathing or wheeze if he develops an infection that affects his chest.
Babies have an immune system related to maternal antibodies to it is very unusual for them to get strep throat, however if you are at all worried about the health of your baby then get him checked out.
He is too young to be self treated at home with tylenol and if he develops an infection then he may need antibiotics.