I don't know about your builder, but he sub contracted that well drilling to someone else. This is the person you need to be going after. In my many years of drilling, I have always promised sand free water. The water quality was left up to God so I couldn't promise what kind of water I would find.
I would stay on this until the driller comes out and does something to stop the sand or you will have problems from now on. Plugged aerators, washing machine hoses, toilet fill valve problems etc. The pumps impellers will also be damaged by sand.
If this is a screened well, he may have over screened the well. He can pull it and change to a smaller slot size. If it's a rock well, sometimes blowing it with a compresser for several hours will solve the problem. But no matter what, something needs to be done.