Sleep didn't seem to help, although everytime he opened his eyes, Percy wanted to go back to sleep because every part of his body was hurting. However, the hallucinations were gone, and he was somewhat coherent. It wouldn't be long before he could go home, pain or no pain.
When Cass asked the question, the first instinct was to lie, because if no one knew how he really felt, then he could go home. Then, he decided that it didn't matter. The moment he was able to move he would leave with or without the Healers' permission. "I feel like a dragon landed on me, other than that, I'm fine. What about you? Ready to admit that you're fine and you should go home?"