I am a non-native English speaker. I have been learning English for a few months. Some people say that "should" is the past form of "shall" but some people say that it is not true. I have asked this question because I was reading a novel and in the novel I found something which looks wrong to me.
From the novel:
I managed to nod. I should say something. I just wasn't sure what to say. He was waiting on me to speak. “I like them,” I blurted out nervously.
As per my opinion:
I managed to nod. I should have said something. I just wasn't sure what to say. He was waiting on me to speak. “I like them,” I blurted out nervously.
My question is that the writer should not have used "should" for the past action. It should have replaced by "should have".