Arcturus, being very familiar with Sirius' flying capabilities, thought that this was quite unlikely, but he let it go at once. The situation was far too urgent for him to press the matter, and even if it hadn't been, Arcturus was of an age where he rather admired the younger boy's quick thinking. It might well be true, and so he'd treat it as such. He nodded. 'Thank you,' he said, his brow furrowing again in concern. He'd had similar flying accidents himself, so he knew how painful they were – except that he'd had them at Hogwarts, where there was a clear course of action. Take the injured flyer to the infirmary, where a dose of Skele-Gro would mend things without any further trouble. Unpleasant enough to go through, but straightforward.
What was he to do here? He didn't have the potion. He didn't have a trained healer to call out on a visit. And yet he had to find a solution. He had to do something, because one of the Hamiltons might suggest taking Sirius to that frightful medbay place, and then he'd have an argument on his hands. No. Arcturus had to show that he was in control of the situation. He cradled the injured Sirius to him, and looked back to Philip.
'I need you to do something important for me,' he said, his voice level and serious. 'I am going to bring Sirius inside, and I need you to go upstairs, and find his bedroom, and bring the best blanket you can find there down to the drawing-room for him, alright? A nice big one.'
Then he turned back to Sirius, getting his attention. 'Siri, we're going inside now. Can you walk in? Are you hurt anywhere else?'
Sirius nodded, because yes, he could walk in, and yes, his side hurt too, and his leg where he'd fallen, but not nearly as badly as his arm did.
Not knowing quite how to take this, Arcturus helped the little boy stand up, and then picked him up anyway, staggering a little under his weight, but managing. Then he looked to Alexander. 'Hamilton, when we're in will you sit with him while I look in my study and see if I have anything that will help him feel better?' Keep him company, he meant. Distract him from the pain.