How was he sleeping previously? Does he fall asleep himself?
If the wakings are new and he usually sleeps throught the night with no help to get to sleep then this is my advice.
Have a chat to him about the bad dreams in the morning when he first wakes up. Ask if he can remember that he had a bad dream and then reassure him that it was only a dream. if he remembers it, then talk it through with him.
Then (and don't think I'm crazy) go out and get him a dream catcher, let him choose it, then when you get home explain that it is a special thing to hang on his ceiling and it will take away all the bad dreams. Make a rhyme or song if you like, but really emphasize the fact that it will help keep his dreams away during the night, tell him that it will bring nice dreams.
This is what my sister did for her daughter and she was under 3. It worked for her, honestly.
I think that we have dreams because we are remembering things that are happening in the day and if you can instill into his dreams that he has something that will give him nice dreams then it might work.
One night my niece woke crying and my sister went in to her and she said that she had a dream and my sister said, 'that's strange, I wonder why the dream catcher didn't keep them and send you good dreams. When they turned the light on, the dream catcher was on the floor!!! It's true, I'm not a superstitious person, but I think that they work if we tell the child a story about them.
It's worth a go isn't it, what do you have to lose? A few quid for a dream catcher!