SunShine - First I feel that you really care about your boyfriend because of the way you wrote the dream and background information.
The dream could be a replay of a motorbike accident he had in the past, but I don't think the dream is really about that. It seems to be a way he has dealt with something that he has survived okay from but really shook him up. I wonder when he dreamt the dream, because it could easily be about the emotional crash he had when his wife died. Even now he could be digesting the experience.
You see, every person we love or have a relationship with mean that we have taken in millions of bits of memory, lessons learnt, life experiences along with all the feelings or problems met by loving and living with someone and they are what makes you the person you are. The memories and experience we gather unconsciously change us and are not lost. It is part of you and is symbolised in dreams as a person or event.
So your boyfriend may be 'digesting' all that he has gathered from his wife. See
http://dreamhawk.com/dream-dictionary/digest/ That the dream accident happened near his mom's house shows how much feeing he has for his mom and how he links with her when in trouble. But remember that dreams use images of people to represent their feelings - for instance feelings and lessons learnt. But you also need to realise that the mother represent and love and care the mother gives, and because he has love for you then you become his mother in some degree.
The motor bike injuries also represent what he felt about himself - his self confidence or his self image - all must change slightly when a big life event or change occurs - and if it is not about the loss of his wife it is certainly about a big change. If he can, it might be good for him to use
http://dreamhawk.com/dream-encyclopedia/acting-on-your-dream/#BeingPersonTony
