How Should An Ear Lump With Pus And Redness Be Treated?

Dear sirs, My baby is 10 year old and he has a lump in his left ear (in outer year-Pinna). its is half pea size lumb. its is since last 4 weeks time. it earlier started like a heat boil and one day a tiny drop whitish buz like substance came and later the bubble changed as normal skin and now it is readis lumb. Pls give us your valuable suggestion.