I read something somewhere recently that on average shrinking is about 2% in fabrics. I'm sure poor quality fabrics are more. I think you will be ok. I would just not wash it. Use it like it is. Then you will have some nice use out of it. When it finally does need a washing you can go ahead and give it a shot and wash it. If it does shrink some you will at least have got some good use out of it in the correct size.