Years ago when my children were small, I would have freaked out. Now, I realize he was enjoying a sensory experience, learning about wet, slippery, oozy paint and naming all the colors.
The nurse gave him a ring pop (which he loved) while she wrapped the cast on his arm. He was happily distracted. Upon completion, she said, "Okay, there you go Liam. It's all yours." He looked curiously at his cast and said, "Oh?" Then he realized what she meant, and he said, "OH!" NOOOO! But as we walked through the hospital he stopped and showed everyone his cast. He has asked twice to take it off, but otherwise he has adapted well and is still his happy little self.
We creative types must adapt, too. If one style doesn't work, try another. If your story isn't working as prose, try writing it as a poem.
Liam is very polite. He says, "God bless you," if he hears someone sneeze, then he says, "Thank you! You're welcome." He told the man thanks and off he ran to us to brag about his apple. Be grateful for the smallest things. Appreciate what you do have, instead of complaining about what you don't have.