At Sirius' concern Peter glances up and blinks in an owlish fashion, surprised and confused by the concern. Pompfrey had also been concerned over it, but the woman could only lecture softly at him as it was all his own doing. Nothing inflicted on him by others. At least, she didn't know all his cleaning was on orders at home.

"Hmm? No. Well, it might ache or itch a little, but that's alright." He said, shrugging as he sat up and shifted on the bed. Ready to help his friend. "Take off your shirt? I'll try to be quick and not hurt you."