new puppy and cat of 13 years help?

Heya, we have had our beloved cat for like more than 13 years and have very recently got a new puppy, its a little shih tzu and we are having trouble with our cat; he attacked the pup one day when it was merely sniffing around and the yelping of the pup made me cry! Our cat wont come in the front room now and just sleeps and stays away in the kitchen and side room. Just seeking any advice you may have? please don't suggest getting rid of the pup or the cat because that's not an option :(