What Causes A Hard Nipple Lump With Pus, Tenderness And Irritation?

My daughter (10 years old) left to spend the night with friend fine .I saw her naked that morning when she got out of shower and nothing was there. She came home today and lifted her shirt and her right breast has a red hard lump to bottom of her nipple and is tender.Then she showed me a little white bump forming at her nipple.She pushed down on it and milky white puss came out of it.The more she squeezed the more came out .It became to tender and really irritated so I told her to stop.The hole of her nipple looks as if it is caved in or something.what is it and do I need to go to hospital.She doesnt have a fev er or vomitting.