"Sterile" is a medical term which means that there are no germs on something. Things like needles, bandages, surgical tools, etc. in a hospital all need to be sterile. It's a good thing when you use "sterile" to describe tools like these.
However, when you describe a place (like a hospital or someone's home) as "cold and sterile", it's not very positive. It means that the place doesn't feel relaxing because it's too clean and uncomfortable. In this case "cold" doesn't refer to the temperature; it means that the place is emotionally cold.