You guys my dog Potato tried to bite my niece's ankles and I'm so sad

I just got Potato about 2 weeks ago and it was his first time meeting my niece. He was barking CRAZY and charging at her so i dove on the ground to hold him back. In public he's a chill guy but when someone comes in the house he always barks (assuming territorial). For now, i figured I'd put him in the kennel BEFORE my niece walks in the house. Is this the correct way to go about it? Is there anything I can do to help him chill out when she comes over i understand some dogs are just not good with kids, but if there's a way to correct it I'd like to try. He is neutered and about 5 years old.