Slightly damaged head gasket
Looks like it got folded/creased. Once the coating is compromised like that, I wouldn't run it. If/when it lets go, you'll be into it for another head gasket anyway, plus a manifold set, gallon of anti-freeze and another oil change; and another weekend of unhooking exhaust, hoisting a manifold and head on and off over the fender, and Neosporin for your knuckles. Get the gasket now and avoid the hassle and aggravation. At least they're sold as singles, so you don't have to get a set.