If there was any truth in what you are saying, I would be worried.
If there were any truth in what you are saying, I would be worried.
What is the difference between them?
Technically the "were" form refers to the past, while the "was" form refers to the present. But in this use the "past" is the time, probably just a moment ago, when the other person said whatever s/he said. In both cases this is in the subjunctive mood, denying implicitly that there in fact is any truth in " what you are saying". Thus in this specific case, there is no significant difference in meaning.