Thermometer for 1 year old

What’s the best way to take a 1 year olds temp? I know they say rectal thermometers are better for newborns and infants. My son woke up this morning and his head was warm and his hands felt hot. I checked under his armpit and it said 99.2. He vomited yesterday but wasn’t running a temp and his behavior has remained the same. Maybe just a little more fussy than normal. I think it’s all caused by teething but just wanted to know if checking his temp in his armpit is accurate at this age