Whats this painful lump on my butt?

i have this sore, or something on my butt and it hurts so bad. I sometimes get these "zits" on my butt (i know gross) but theres usually only one at a time and its pretty small and i can pop it and it goes away. But with this one, its really concerning me because its about the size of a quarter and it sticks out a lot. I cant sit without it hurting like a mf. It has a kind of brown center and then the rest is red. Can anyone help please?? I dont know why this stuff happens to me!