Pain is way too general. The argument you and your friend got in, I'd have to say you were both right. Pain can be physical, but it can also be emotional. Physical pain is when you break a leg or something, and you react by yelling, or crying, or something of the sort, to release the bottled pain out. Emotional pain is a heartbreak, which is usually dealt with by crying or talking about it. It's all inside, but, in my opinion, it can hurt much more than physical pain can.
But, it's both an emotion and a physical response.