Your pix is too fuzzy. If the opening is a cut, and the carcass is cut, the tire is nearly toast. Minor nick to the carcass: boot the inside, shoe goo or
goop the outside and use it on the rear only. If the opening is a manufacturing defect in the rubber alone and the carcass undamaged, just goop
the hole and use as usual. "minor nick" means only partial thickness cut to a few threads. If the area bulges even a tiny bit under pressure, trash
the tire. Sdewall damage can be minor or significant and not be a lot difference in appearance. Many tires after a 1000 miles or so will have a
few nicks in the sidewall from hitting rocks, for some riders this is instant toss but my experience is that a few mm long cut that doesn't penetrate
full thickness or bulge is safe. Your case depends on what the carcass looks like inside and out.