Several people I know who have serious heavy metal toxicity issues get lots of burning feelings on their skin. Not sure if that applies to you.
The fingernails are related to either mineral deficiency, fungus in the body, or low adrenal levels. I forget which, but there is a picture chart I saw at a health expo (possibly from Chinese medicine) that labels the conditions associated with how nails look.
Here's sort of a general description without the pictures: http://noreen-kassem.suite101.com/how-fingernails-indicate-health-problems-a146188