Truth

In class we discussed Kierkegaard's idea that everyone can only be sure of one thing, that they know nothing. Which brings up his next point that truth is unique. That truth is different for everyone. That everyone has their own idea of what is true and their truth helps form their identity. This relates to the idea that people only know that they know nothing because if no knows anything for sure and everything can be doubted then there is no truth. Truth is someone's own interpretation. This kind of scared me. Is there really no universal truth? Doesn't this idea mean that everyone can go around doing what they want because they think it is true. That any person can win any argument because what they think is true and nothing else can change their mind. This makes me think that everyone therefore is just ignorant in Kierkegaard's theory is true. But is it true? Or is it just something else that should not be taken seriously because it is only his truth, and no one else.