You should read the label on your sofa cover for cleaning instructions.
Generally speaking if it's made of synthetic fabric like polyester, medium to low temperature drying isn't a problem. From my own experience, it's also OK to dry cottony products with medium to low temperature, it will have a little to none shrinkage, but nothing significant that I couldn't afford. However if you want to be absolutely sure, wash it but don't use the dryer. The only problem is that you'll need to iron out the wrinkles.