Klaxon - sporn lovers - what is this?!

[PrincessOnTheInternet]

Had a really sore spot on my armpit, squeezed it, got nothing. ( ) In all my poking and prodding, some pus came out of... somewhere - a thick, almost luminous yellow ball. Squeezed again and got some bloody yellow pus and in my fingers it felt a bit... powdery?
I usually get this about once a month, at the same sort of place in both armpits and lots of pus. My question is, if there's no visible lump or spot there, where is this pus coming from?

Sorry if tmi. Wish I could get a picture or video to show -- know its 'the usual' on these threads but I never can plan to video it as it just randomly happens while poking!

It sounds like a cyst. The stuff you get out isn't pus but macerated skin cells and keratin. It will recur until the lining is removed, the lining is like a sac of skin trapped under your actual skin, it's trying to act like skin by producing new cella but it can't because it's inside IYSWIM. they can get infected and then you'll get pus and skin stuff. The more you prod it, the harder the sac is to remove as it gets scarred.

Thank you mrsmorton