We've seen two instances where the Queens have obviously manipulated others, and trying to overcome that manipulation resulted in headaches.
Back in SMALL FAVOR, when Harry almost inadvertently remembers using fire magic.
On the opposite side of Ivy, Rosanna launched more traditional lances of flame from her open palms, much like the ones I— —a savage pain went through my skull for a second—son of a bitch— —but Ivy dispersed them with delicately applied wedges of air, intercepting each burst of fire far enough short of her body to prevent the bloom of heat as they died from scorching her—though the two more physical Denarians who strained to force their way past the barrier of snapping sparks that formed whenever they tried to get close had far less luck.
And in SMALL FAVOR, when he actively tries to recall what a blasting rod is.
Pain stabbed me in the head, ice picks plunging into both temples. I flinched and doubled over. Blasting rod. Familiar words. I fought to summon an image of what went with the words, but I couldn’t find anything. I knew I had a memory associated with those words, but try as I might, I couldn’t drag it out. It was like a shape covered by some heavy tarp. I knew an object was beneath, but I couldn’t get to it.
Which is also reminiscent of Lily trying to work around Titania's manipulation.
“I know,” Lily said. She lifted her hand to a temple and closed her eyes in a faint frown of pain. “But…’’ She shook her head and fell silent again as Titania’s binding sealed her tongue.
Which is somewhat similar to what happens to Harry when Mouse tries to give him the idea to use
him to search for Thomas.
Mouse pawed at my leg and looked up at me. I bent over to scratch his ears, and instantly regretted it as someone tightened a vise on my temples. I straightened up again in a hurry, wincing, and entertained wild fantasies about lying down on the floor and sleeping for a week.
Harry even realizes it later, when he confirms with Mouse that he intended to help Harry.
“Earlier tonight,” I said, “when I was trying to figure out how to find Thomas, you interrupted me. I didn’t think about it before now, but you helped him track me down when Madrigal Raith was auctioning me off on eBay.”
Now, if you'll note, if there were a compulsion to try and stop Harry from using Mouse to find Thomas, it must have stopped working for Harry to have that clear thought. Which means either he was manipulated, and it was just a conveniently distracting headache, or the thing that was needed of him was already done.
That's where the theory not previously mentioned by me (that Mab wanted Harry to bond with Demonreach) comes in to play. Since Harry couldn't find Thomas, he decided to face Shagnasty mano-e-mano. And to do that, he went to the island and completed the ritual. And
after that has been done, Harry can suddenly realize what Mouse was trying to do.
That may not have been the linchpin moment. Maybe something else happened to release the compulsion from Harry. But that's what others have suspected might be the motivation for such an action from Mab.