what finger are you supposed to wear a ring on if your single and just like wearing rings?

I bought a ring from pandora that im thinking of returning anyways cause i dont feel like wearing it and it was a waste of money. but i got it sized to my left ring finger and like im assuming thats the ring your supposed to wear a ring on if your married or something? because i went to work and my boss looked at my finger and was like "whats that" im like "oh i just bought it" and shes like "oh i thought something was happening. what finger are you supposed to wear a ring on then?