My cat just fell out the window...

Your cat could have a fracture or other potentially serious injury, I would take the cat to the vets for a general check-up.

The cat may get better over time but in my opinion it's better to be safe than sorry. Unlike humans it's very difficult for a cat to complain to you about how painful it is to run around all day on a once-fractured leg.

I'll 1+ on that, you'll never know, it might be broken and the cat is just trying to 'deal' with it, unlike us human who moan at the slightest paper cut.