This is the 10270th most frequent Russian word.
больное
The Russian word "больное" means "sick" or "ill" (neuter form).
In this sentence, 'больное' is used as an adjective describing 'место' (spot), conveying the notion of emotional pain or sensitivity.
Это было больное место для него.
This was a painful spot for him.
Here, 'больное' is used in its masculine form as 'больном' to describe 'друге' (friend), indicating that the friend was ill.
Он всегда заботился о больном друге.
He always took care of his sick friend.
In this context, 'больное' modifies 'время' (time) to signify a period characterized by emotional or psychological pain.