This is not a complete sentence; there is no verb. There is no need for either first-word capitalization or punctuation.
No need, but it can be an answer to a question, so it's definitely not wrong per se.
Co leży na stole? Brudne noże i widelce.
Przepraszam, I was being anal retentive on that one.
Why not filthy?
Ok, let's add it.