Seriously... it's probably OK for normal driving, but let me relate a situation that happened to me. I had a similar damage on my front tire and I decided to drive home (50 km away ) and not put on the spare and get a new pair in the morning (I'm just OCD about tires that don't have matching threads...).
During the drive I had to make a high-speed emergency maneuver, to avoid a stalled car in the fast lane, which put all the weight of the car on the side of the tire. As you know, in a quick slalom the weight of the car shifts left/right. As soon as the weight came down on the tire, it compressed and the tire blew.
So, you're taking your chances. There's a few things I never mess around with... tires, brakes, ball joints, engine oil, etc.
Oh and, perhaps this is ironic, it happened to me in my old 2004 Mazda3 which I traded in for the Accord I currently own. The tires had 44,000 km on them. Those stock Toyo tires = shyte.