Problem Online

So a woman on Reddit posted she was interested in online sexual contact with someone. Her profile said she was 27. I am 25. She sent me a half naked picture and I sent her a nonsexual picture of what I looked like. We gave each other titles. The woman in question, while looking like an adult, looks young and skinny enough that it makes me think she could be underage. What is the law on this matter? What should be done?