:zaahir hai;N merii shakl se afsos ke nishaa;N
;xaar-e alam se pusht bah dandaa;N gaziidah huu;N
1) the marks of sorrow/regret are apparent from my form/shape
2) through the thorn of pain/grief, I am [with] a tooth-bitten back
pusht-e dast bah dandaa;N gaziidan = In a state of grief and sorrow, to bite the hand with the teeth [Zamin's text has juu;N shaanah pusht-e dast]. The meaning is clear. The simile of the comb's hand being teeth-bitten is only for the wordplay of teeth, since a comb too has teeth; otherwise, for the presentation of the meaning it was unnecessary.
The teeth of a comb are the 'back of its hand' [Gyan Chand's text has juu;N shaanah pusht-e dast], and also its teeth. So to speak, the teeth have bitten the back of the hand. In pain/grief, the back of the hand is bitten with the teeth. In this way, in the external shape of the comb the marks of grief/pain are found. On my face too this kind of contempt rains down. Seeing my tear-marked face, my sorrow and grief can be guessed. So to speak, I too have bitten the back of my hand with my teeth.
SETS == IDIOMS
For more on Ghalib's unpublished verses, see the discussion in {4,8x}. See also the overview ind ex.
There are variations in the manuscripts that considerably reshape the second line. The commentators agree on juu;N shaanah pusht-e dast bah dandaa;N gaziidah huu;N . Raza gives the text as above, and recognizes as a variant maanind-e shaanah dast bah dandaa;N gaziidah huu;N . I am not going to get into all the textual variants at present, I am just going to follow Raza (who in turn follows Arshi, see p. 64).
But the existence of the variants is helpful, because it makes it clear that Ghalib had been playing with the Persian idiom pusht-e dast bah dandaa;N gaziidan , 'to bite the back of the hand with the teeth' (to express extreme grief and sorrow). In Raza's preferred text, that idiom is at most only evoked or alluded to, but in the other variants we can see it more clearly. And in the other variants there had been juxtaposed to it the word 'comb' [shaanah], so that, as Zamin says, 'the meaning is clear'; the commentators explain it easily.
But in Raza's choice for the best text, the word 'comb' has been omitted (though with its teeth perhaps suggested by the 'thorn'), and the word 'hand' too is missing, so that the speaker has only a 'tooth-bitten back'. Although for the present I'm not going to do the necessary research-- as a small sample of the complexities, see the Anvarul Haq Hamidiyah edition, p. 122-- I'm betting that he went from the more clear and straightforward versions to Raza's obscure one. It would be just like him, wouldn't it?
Raza's version makes me think of an emaciated lover bowed by pain and suffering, so that the vertebrae on his spine stand out and make his back look as if it has been nibbled by the teeth of some cruel predator. If not that, then what? In the absence of 'hand', there aren't enough hints and signs left to evoke the idiom (in Urdu as in English, the 'back' is really quite different from the 'back of the hand'). Has the ambitious young poet perhaps outsmarted himself, or (so to speak) over-rotated? Perhaps so. Still, Faruqi marked this verse as one of his choices. You, dear reader, can decide for yourself.
Asi:
The marks of pain/grief are becoming apparent through my face and form. So to speak, I am like a comb that bites the 'back of the hand' with its teeth [Asi's text has juu;N shaanah pusht-e dast].
== Asi, p. 172