ESR is something called an inflammatory marker. It's raised when there's some kind of inflammation or infection going on in the body. However, there is large degree of natural variance between people and can fluctuate with age, weight etc. I think an ESR of 17 is only barely raised - for example; elderly people can sometimes have an ESR of around 30-50 without actually having anything wrong with them.
It's impossible to tell what it is that is wrong without knowing all the other test results, but I'm sure with an ESR that low that nothing much coould be the problem. I expect it is an automated machine that flagged the value as high, I don't think a doctor would think an ESR of 17 would be something worth worrying about if there were no other signs.
If you are intersted, ESR stands for erythrocyte sedimentation rate, the time it takes for a blood sample to settle out into layers. Inflammation changes the viscosity of the blood hence changes the ESR.
All the best