sham((a huu;N lekin bah paa dar raftah ;xaar-e just-juu
mudda((aa gum-kardah har suu har :taraf jaltaa huu;N mai;N
1) I am a candle-- but with the 'thorn of searching' gone into my foot
2) having lost the object-of-search, in every quarter, in every direction, I burn
just-juu : 'Searching, seeking; search, inquiry, quest, scrutiny, examination, investigation'. (Platts p.381)
mudda((aa : 'What is claimed, or alleged, or pretended, or meant; desire, wish; suit; meaning, object, view; scope, tenor, drift; — object of search, stolen property'. (Platts p. 1015)
jalnaa : 'To burn; to be burnt; to be on fire; to be kindled, be lighted; to be scorched, be singed; to be inflamed, to be consumed; ... to feel pain, sorrow, anguish, &c.; to burn or be consumed with love, or jealousy, or envy, &c.; ... to get into a passion, be enraged, to rage'. (Platts p.387)
That is, I am a candle, but a kind of candle in whose foot a 'thorn of searching' is lodged, in such a way that it has forgotten its original object of search and what it ought to do. Madly I go groping around in every direction, since somewhere the sought-for pearl might come to hand. For this condition he has given the analogy of a candle of which the wick (thorn) has come out and has begun to burn from both directions. The rareness of the analogy is worthy of praise.
bah paa dar raftah ;xaar-e just-juu = in whose foot a 'thorn of searching' is lodged. The wick of a candle is called the 'thorn of the candle'. Poets have made for 'searching' the metaphor of a thorn that has lodged/pricked in the foot. I am the kind of candle whom the pricking/anxiety of/for search is tormenting. I wander in every direction. Far away from the desired goal, I am stumbling around this way and that, and along with this I am also burning.
For more on Ghalib's unpublished verses, see the discussion in {4,8x}. See also the overview index.
On the 'thorn of searching', see the discussion of similar 'foot of' expressions in {152,3}.
As Gyan Chand notes, the wick of a candle is called the 'thorn of the candle'. Having a thorn lodged in your foot means that you're in constant pain, and trying to walk only aggravates the pain, so that you're distracted and unbalanced. If you're a candle with a single, round, symmetrical 'foot', walking would be impossible, and so would extracting the thorn/wick-- all you could do would be to writhe and 'burn', and that too in all directions indiscriminately, since your round 'foot' couldn't move you in any particular direction.
What the verse really creates is a Siamese-twin melding (two tenors and one vehicle) of two separate metaphors: the candle-wick is a thorn (in shape, and since it causes the pain of burning), and an obsession with 'searching' is a thorn (painfully and unignorably lodged in one's foot).
The flexibility of jalnaa (see the definition above) is also effective. The candle might 'burn' with 'pain' (from the thorn); or with 'love' (for the beautiful lost beloved); or with 'jealousy/envy' (since the lost beloved might be with others) or with 'rage' (at the loss of the object of search).
Asi:
I am a candle, but a candle that, while searching, has hade a thorn lodge/prick in its foot. Now I have lost the object of search, and am burning in every direction and am wandering around. That is, I am a candle, but I have become only a 'candle of searching' and have lost my object of search.
== Asi, p. 177