If I use results from a source I don't have access to, should I include it in references? Let's say, I am writing a paper. I am reading paper A that cites results in Paper/Book B. I do not have access to Paper/Book B. 

In the list of references, do I include only A? A and B?
Be honest. You do not gain anything by pretending knowledge you have not, nor it helps the reader. 

Write "According to A, in B it is shown that" or some variation on it. If you have made a good-faith effort to obtain a copy of B (that includes interlibrary loan), but had undue difficulty in doing so, you might want to mention it --- "We were unable to find a copy of B".