Porn sites appearing in my stats referrers

[QHF]

I have a question about something I found when checking AWSTATS from cPanel. Near the bottom is a section called Referrers with two headings:

1. Referring Search Engines and
2. Referring Sites

A porn site is listed under the Referring Sites heading and I'm not sure exactly what this means. I haven't received or seen any porn sites coming into our domain, so, can you tell me if this is something I should be concerned about?

QHF