The significance of the quote depends on understanding the plot. The conflict is internal, in the narrator. We can tell from the way he talks that he is tough and practical and can't be bothered with anything beyond the superficial. In the course of the narrative, we learn that he drinks a lot and smokes dope, isn't the religious type, and certainly isn't the touchy-feely type. But at the end, Robert convinces him to draw a cathedral with him. When he really gets into it, Robert tells him to close his eyes and keep drawing.
So we kept on with it. His fingers rode my fingers as my hand went over the paper. It was like nothing else in my life up to now.
Then he said, “I think that’s it. I think you got it,” he said. “Take a look. What do you think?”
But I had my eyes closed. I thought I’d keep them that way for a little longer. I thought it was something I ought to do.
“Well?” he said. “Are you looking?”
My eyes were still closed. I was in my house. I knew that. But I didn’t feel like I was inside anything.
“It’s really something,” I said.
At this point, he identifies with the blind man, and in a sense sees the world through his eyes (as a place of wonder and fascination). Even when Robert tells him he can open his eyes, he doesn't do it. All he can say is, "It's really something." It does not matter what they've drawn in the end, or how it looks. The narrator has just had his first enlightened moment, his first spiritual experience.