S. R. Faruqi:

By 'the night's breast-clawing' is meant the previous night's breast-clawing, because to reserve only the night for breast-clawing (that I used great skill in breast-clawing at night) has no meaning. The point is really that we keep on doing breast-clawing all the time, and in last night's breast-clawing we used great skill, in that our sharp and pointed nails devoured both heart and liver.

The idiom khaa gayaa as an image he has used very well. In calling the nails sar-tez there's also the implication that because of the intensity of madness he hasn't had his nails trimmed, and they've grown out and become long and pointed.

To provide for the tearing of heart and liver the term 'skilfulness in breast-clawing' is also very fine. He's used exactly this aspect in the first divan as well [{384,4}]:

har ;xaraash-e jabii;N jaraa;hat hai
naa;xun-e shauq kaa hunar dekho

[every clawing of the forehead is a wound,
look at the skill of the fingernails of ardor!]

[See also {297,2}; {1590,1}.]

FWP:

SETS == GROTESQUERIE
MOTIFS == LIVER
NAMES
TERMS

Last night's 'art, skill, craftsmanship' apparently reached a new hight of excellence, because when both the heart and (especially) the liver are entirely clawed to pieces or 'devoured', then surely life is over. For while the heart constantly consumes blood, in the ghazal world the liver is the blood-maker, the emblem of fortitude. So this may be almost a 'dead lover speaks' verse.

In any case, this verse is an example of what I call 'grotesquerie', in which the physical literalness of the imagery becomes distasteful to the imagination. It's routine in the ghazal world for the heart and/or liver to be destroyed, lost, pierced with arrows, etc., but to imagine the fingernails bloodily clawing open the whole chest and then gradually, systematically, skilfully clawing to bits and 'devouring' (like an eager predator) both heart and liver-- well, the idea is basically off-putting, or even actively disgusting. The contrast between the bloody wreckage of the clawed-open chest, and the savoring of the 'art, skill, craftsmanship' used on it, is just too over-the-top; for my taste, it's too distracting and repugnant to be enjoyable.