Not sure without seeing it, but irritation or eczema seems most likely. I can't think of a skin condition that looks like this that would produce sharp pains. If those continue, you'll need to see a doctor about them right away. If the rash persists another week even if you leave it alone and just moisturize, as I advise you to do, then you'll have to show the rash or spot to a doctor in person.
Best.
Dr. Rockoff