Black mark inside my screen

[Barbal]

A small line with a fern like blob on the end has appeared inside my screen. Has anyone ever had the same problem?  Anyone have any idea of what I can do about this please. My Bravia TV is out of warranty. 
Thanks

[royabrown2]

@Barbal 

Can you post a screenshot, magnification as high as possible?

Thunderfly?

Trail of failed pixels?

Our sone diagnosed the latter* on a four year old TV with a five year warranty; and as they couldn’t fix it, they gave us a full refund to use against a new TV. So we were able to get a much better one, and still have change.

*He could see it with the naked eye; I needed a magnifying glass to see what it was, exactly 🤓