S. R. Faruqi:

ru;x.sat = permission
minnat = kindness

As a result of resting the head on the beloved's feet, for the burden of kindness to be laden upon his own head-- this thought in itself is very fine. But it's not made clear in the verse whether he did rest his head on the beloved's feet, or did not. In the verse there's mention only of the permission. It's possible that this permission itself might be enough to make the lover happy and make him indebted for kindness.

Since 'now' also refers to the future, there's also the implication that this obligation remained on his head in the future.

FWP:

SETS == EXCLAMATION; INEXPRESSIBILITY
MOTIFS
NAMES
TERMS

Mir uses the same idiom in

{700,11}

too, taking advantage of the complexity of ghar ; here, he takes similar advantage of the complexity of minnat , with its double meanings of the 'kindness, favor' shown by the giver, and the 'grateful thanks' incumbent upon the recipient (see the definition above). Just as a metaphorical burden of moral responsibility can rest on the head in English ('If that happens, on your head be it!'), a metaphorical burden of gratitude rests on the head in Urdu.

It's an enjoyably double-sided transaction-- the lover's head is placed on the beloved's feet, while in the same process a heavy 'burden of gratitude' is placed on the lover's head. And to the lover the transaction is a powerfully emotional one, one with an impact that can hardly be-- and should not even need to be-- described in words ( kyaa puuchho ho ).

But what kind of emotion is involved? Is the lover exclaiming with rapture about the beloved's kindness, or ruefully recognizing the immense burden of obligation that will be 'on his head' from now on?