I can't give you a perfect answer that's definitive, but I'm afraid you are just starting to age!
I started to get my first white hairs on my beard when I was 25, which I thought was odd... and I also found maybe 7-8 white chest hairs then.
Since then I am getting some white hairs on my head as well, more than I would like being only 28.
I think there is often a misperception that people don't grey until their 40's, but I asked all my friends my age and my doctor, and they are all getting white hairs too... everybody is different when they start to grey, I know people who began to grey when they were 19!
A doctor told me it is very individual where on your body you will begin to grey and at what age, but it doesn't necessarily mean something is wrong.
I would bet you're fine, but if you're very worried, go to the doctor.