My six-year old daughter three weeks ago had a pink small bump on her arm, didn't itch, no fever, that then developed a whitehead on it, I popped it, came out a lot of white pus, just like a white head now it is purple, not raised but has some small little white/pearlized color bumps around it. It is also hard underneath no fever, doesn't itchit she says it doesn't hurt. What is it.