He notices the look and tries to sound reassuring.

"We'll worry about that if it happens. Right now, it's better to make sure your ankle heals quickly. Besides, once it's recovered, we should be able to reuse everything, right?"

It's just cloth and part of a trombone, after all. He'll carefully reach out to hold Simon's foot in place as gently as possible. He... might also be blocking the view of all the blood on that cloth tied around his left hand with his right. No need to freak out Simon any extra.