How to prevent home-pierced ear infectio?

okk so today my friend piercd her own cartilage nd i wuz stupid enough to just dew a 2nd piercing like where u regularly get it donee but i stuck the earring where i had it done before like when i wuz 7 (nw im 13) but it closd nd there wuz still like a mark were itwuz, nd it didnt hurt at all when i did it the first time but i put a bigger earrin in and i dnt wnt my parents to freak soo how can i make sure it does get infected with out usin tht alcohol stuff?