I have a question about wearing a ring on your left hand?

I have a beautiful ruby ring with little diamonds on it and I wear it on my left hand. Although I do have a live in boyfriend I am not married. A friend of mine recently said that I shouldn't wear my ring on that hand because of the symbolism of marriage. My boyfriend said that he could care less. I plan on wearing it anyway because I don't care what people think but I'm just wondering if it is improper somehow in our culture to do this.