Robin asked because it's a little hard to tell... Not just because Phalanx doesn't seem to be reacting, but also because they don't seem to feel it in the way that normal humans do. The hurt is there, but it isn't connected to them, because the hand that's bleeding isn't really connected to them either.

So he tilts his head a little, considering how to answer, eventually settling on a simple, "A little."

He pins each of the removed needles into his own shirt sleeve to get them out of the way. Phalanx can keep the bobbins and bits of thread, but all of the sharp things are being taken away.