Old Norse is a Nordic langauge, which makes it a North Germanic language, which, in turn, makes it a Germanic language.
Nordic languages (a family of languages) are descended from Proto-Nordic (a language).
Germanic languages (a family of languages) are descended from Proto-Germanic (a language).
Germanic languages are Indo-European languages, which have Proto-Indo-European as a root language.
You are not wrong in saying that Proto-Germanic and Old-Norse are IE languages. But it's also like saying that nickles and coins are currency, it doesn't mean that nickels are not coins.