I’m sorry to hear that! I don’t know much about Graves disease but that sounds like a difficult time in your life. It’s important that you focus on getting better from your car accident before you start worrying about the gym or even your weight, though.
If you still can’t get it off your mind, are you allowed to take walks? Walking might help assuage the anxiety you are feeling in relation to not being able to hit the gym. You’re doing cardio while getting sunlight and fresh air! Nothing better in my opinion!