Sometimes nanomachines treat regeneration 'bots as hostile invaders.
Yours were particularly aggressive, and I couldn't do a thing with you other than induce a coma and look for their "standby" switch.
The headache you've got is a side-effect of the coma-inducers.
How about slipping me some "inducers" with euphoric side-effects?
Happy hour begins in about two minutes.
Not for you, Sergeant.