It's a big topic, and it's called "epistemology".

Plato: anamnesis.
Descartes: Doubt.
Wittgenstein: certainty.
Gettier: rational true belief.
This is a brief and incomplete selection of backgrounds to the problem of knowledge in general. The specific problem of the relation of direct v second hand knowledge it is generally beneath the dignity of philosophers to consider - we are all doubting Thomases in that regard. We still haven't established the security of first hand knowledge, without considering what anyone else has to say.

That is a brilliant reply!

I only ask about how second hand knowledge is treated/discussed as i need to write about it in regards to first hand accounts and need to know what research to do lol thankyou for your help :)

Anthologies are a good place to start. Something like:

Epistemology: An Anthology - edited by Sosa and Kim

or

A Companion to Epistemology - edited by Sosa and Ackerman

or


Contemporary Debates in Epistemology - edited by Steup and Turri

how first and second hand accounts and information is treated and viewed — Arran

You might want to look into Kuhn as well. He did philosophy of science with a focus on the fact that science is an inherently social practice. His seminal work was The Structure of Scientific Revolutions.

Definitely read up on the Gettier probem, for sure, as someone else pointed out in here. And as also mentioned, Plato and Descartes are great starting points as well.