My dog is terrified of fireworks what can I do?

My dog ( staff cross with collie age 8) Is petrified of fireworks! We all ways leave the kitchen door open so he can come and sleep in my room. but my mum doesn't like that. so we don't know how to make him less scared. we don't have a crate. is there like a thing that we could do to him to make him not scared? pls help