Hi @Kim229,
I'm sorry to hear about your guest's accident. It was kind of you to cancel but unfortunately there are automatic penalties for cancelling as a host. @Aogán0 has given you a great response with information about the Extenuating Circumstances policy. If you contact Airbnb and explain the situation they should be able to help you.
Just to let you know, I have moved your post here to a new thread so that it doesn't get lost in another discussion and it is easier to find. I have also given it a title, please let me know if you want to change it!
In case you're not sure how to start a new thread - this CC Tutorial gives a step by step guide to starting a conversation in the Community Centre.
Kirstie