What Causes Red Lumps On Chest And Neck?

Hi, my names Paul. I have developed a kind of rash on my back and upper chest. There's a lot of like red lumps on my chest varying in size. They look a bit weltered on top and sometimes turn purple. Squeezing them either does nothing or squirts out puss and blood. Is there anyway I can send u images of the rash by attaching them or by email ? Thankyou