"Because my stomach hurts, I am going to the bathroom."
This can make a research article you know.
Both talks about a casual relationship.
A ので、B 。
You talk about a circumstance A, and in such circumstance an event B arises naturally. There is a strong but subjective association of A and B.
A から、B 。
You talk about an event A which, in your objective view, directly caused an event B to arise.
The difference is actually a subtle one and in many cases interchangeable. However, as beginners, the first thing we are taught to remember is not to use から to explain your fault. You will be conveying the message that the reason you have given is the sole cause of the unpleasant outcome and you have no responsibility yourself at all.
The way was congested, and thus I am late.
My understanding is that ので is also more polite. Check out https://www.learn-japanese-adventure.com/japanese-grammar-cause-reason.html