Can someone please tell me what this is?

i got a new brand of razor & shaved my armpits and a few days later what I thought was a boil appeared under my armpit. I put a warm wash cloth on it and after a few days it eventually popped and drained. Then a few days after that this is what showed up. It’s painful to move my armpit and I don’t know what this is. I keep applying a warm washcloth everyday but Can someone explain?