Nico was sick, he was wearing a skull sweater that was a little too big for him, his nose was slightly red and he had a small box of tissues with him

Nico: no, get away from me, Will, I'm fine

Will: You're sick, sunshine

Nico: no, i'm not sick, I'm a ghost king, I don't get sick-! starts coughing

Will: right, The ghost king NEVER gets sick

Nico: continues coughing exactly

Will: All right, Nicholas, off to the infirmary. doctors orders