He is probably frightened - he thought he was in a safe place, but got beaten up. It is depressing for any creature to lose a fight or get hurt. Keep him warm and reassured until you see the vet.
Do Cats Get Depressed After A Cat Fight?
Give her care and love. Cats are sensitive and they have feelings. It is possible that she is depressed but you treatment her with more care in this time period.
My cat had a fight a few days ago and since then he just sits down with his chin on the floor, is he depresed?