KMy Daughter Has A Lump Under Her Arm Pit It

KMy daughter has a lump under her arm pit it has pus leaking out of and it smells. I've been giving her a hot compress rag should I take her to ER or try to press out pus on my own even though I really don't want to touch it I can't even look at it. But I'll do it just cause it'd my kid. Plz whats best??