That sounds like trigeminal neuralgia. I suffered that for several years, until a dentist finally found a cracked tooth and took it out. The trigeminal nerve comes out from the back of your head and covers most of your face.
https://en.wikipedia.org/wiki/Trigeminal_nerve
A lot of things can cause the disease; they call it the ‘Suicide Disease’, because people have killed themselves rather than live with it. The pain comes on very suddenly and unpredictably - I remember having to sit down on a curb and just cry, simply because a wind hit my face.
In your case, the shingles lesion must have been impacting the nerve, somehow.
(Ben Carson is one of the doctors who has done a lot of good work with this.)
Shingles is mentioned as one of the causes, in the Wiki on TN:
https://en.wikipedia.org/wiki/Trigeminal_neuralgia#Causes
https://www.urmc.rochester.edu/neurosurgery/services/conditions/trigeminal-neuralgia.aspx
I got the shingles while a student at The University of Alabama in 1971.
The clinic Doctor suggested my getting a Small Pox vaccination which I really questioned but saw no risk.
This vaccination CURED it. Since then the medical planners have destroyed that type of Small Pox treatment, unfortunately.
I have had no further problem. The infection is as painful as described on this forum.