Hi,
My son was exactly the same, he screamed the first time we put him on sand. We didn't do anything special really, just took it slowly and didn't make a big deal of it. He is now the biggest beach bum you could wish to meet and loves nothing better than spending the day at the beach.
I think because we were calm and matter of fact about the sand that this eventually rubbed off on him. It takes time, but with our son we tried not to make a big deal about it and in the end he didn't either.
Jools