The best thing for you to do is to keep him calm and in a quiet contained place. Small room, dog cage, or pen with room for a litter tray and food/water.

Check that there is no bleeding elsewhere. Are his ears hot to the touch, does he feel clammy? This can be a sign of a fever, if YES keep him calm and relaxed place him in a cool area. If YES and he's trembling, he has an extreme fever and may be going into shock. Keep him calm and still, talk to him and get him to a VET NO MATTER WHAT! If NO and he's trembling keep him warm.

Make note of what he eats and drinks. When you pinch his skin does it lay flat back quickly or does it seem stiff and stick, not go back to shape quickly? If the latter he may be dehydrated and also in shock.

Once you have answered these questions you need to call an out of hours vets, any vets should have an emergency contact for out of hours. You can speak to them on the phone for FREE! get some advice and give them the details about the cat and the above questions. They will then ask you questions to get a better idea of the situation and give you the best advice you could need, please don't rely solely on the advice you receive here. You need the advice of a vet or vet nurse.

Ideally you need to get him to a vets for care. Hope he's alright.