Hi, thanks it does look like debris as it has a "tail".
"A different type of defect caused by microscopic contaminants within the manufacturing process can also be found. Contamination results in a dark "stain" covering one or several sub-pixels. They are not pixel or sub-pixel defects per say. No contamination is allowed under HP policy."
The problem is that I bought this laptop using a deal which has already expired. Does "return" mean permanent return or an exchange? ... I just answered my own question. So I should ask for an exchange rather than a return?