Itchy/irritated armpits

A few hours ago, my armpits all of a sudden started itching and I’ve obviously started scratching the itch. I’ve now had a closer look and not only are they super irritated but it feels like there’s something underneath the surface (kind of like a cyst but vertically), where the red marks are. Does anyone know what this could be? And how can I relive the itchy/irritation?