I agree, please see a vet ASAP. He could have damaged internal organs, a broken bone, internal bleeding etc. I would be very concerned. I lost Bandit because of an internal injury and I rushed to the vet as quickly as I could gather everything together. Even at the vet, the vet said she couldn’t feel anything wrong with him because he didn’t seem in pain or anything when she check him over, but I knew there was something seriously wrong. In Bandit’s case, it was a ruptured cecum which unfortunately there was nothing to be done about. In your case, since he has lasted the night it’s probably not as serious as a ruptured cecum, but something is certainly not right and an x-ray or ultrasound is probably required to see any organ or bone damage. It may just be bruising, but in any case a vet can still prescribe pain killers which can help to get him eating and moving around again.
Sending best wishes.