I have to admit, sorry to be pessimistic but I think it looks very infected and needs to be treated.
The grey scales look like those I saw recently on another Betta thread who was not so lucky with grey scales through the midsection. He perished, and was never abscessed nearly as bad as yours.
I hope the treatment helps! Is he isolated in a QT tank yet? Not sure if he had tank mates before.
Also, can we see photos of the same side? The grey has not reached the bottom ridge below the tail yet
It looks sadly like he may have fin it through the spine.. I would not be surprised if he loses his tail completely but still recovers, but who knows, sorry to be a downer
The grey scales look like those I saw recently on another Betta thread who was not so lucky with grey scales through the midsection. He perished, and was never abscessed nearly as bad as yours.
I hope the treatment helps! Is he isolated in a QT tank yet? Not sure if he had tank mates before.
Also, can we see photos of the same side? The grey has not reached the bottom ridge below the tail yet
It looks sadly like he may have fin it through the spine.. I would not be surprised if he loses his tail completely but still recovers, but who knows, sorry to be a downer