I had this recently, too. Had never seen anything like it. Mine itched as well as felt uncomfortable from the bubble rubbing against the inside of the eyelid. Don't know what it is, but I tried using Zyrtec eye drops and it has cleared up entirely. "Regular" eyedrops had no effect.
Good Luck!
The air tonometer will not cause this. Call up the Eye doc that examined you and ask the question of him/her
JCHMD