Look at the way hes breathing and the way he's pressing the wound with his hand after waking up, he clearly used the recovery breath he learned from Rengoku to close it and regain stamina, and just as he said in recent chapters he's able to fight using the breath of water since it doesn't take a toll on his body and he can't use breath of The Sun at the moment because of his injuries.
I don't get how there are complains about Tanjirou still fighting when it has been explained before that with mastering your breath you can boosts your stamina and
physical strength