Yes, you need to take your dog to the vet for bruised ribs.
Do I Need To Take My Dog To The Vet For Bruised Ribs?
You'd want to do at least a quick x-ray to be sure the are bruised and not broken. Not sure what happened but if it's hard enough to bruise or break ribs internal injury may also be a concern as well as some other things. Best to go in and restrict activity (kennel rest) until you get there just in case.
Yes, you must. Taking him to the vet is the must to do, in case of serious repercussions.