Its under his armpitits red from lickingwith a small bump?

It sounds like there may be an irritation or infection under the armpit, possibly caused by excessive moisture or friction from licking. The redness and small bump could indicate a skin condition, such as folliculitis or a minor allergic reaction. It's advisable to keep the area clean and dry, and if symptoms persist or worsen, seeking medical attention would be a good idea.