Yes, give it some time and you might get lucky.... but if you didn't get enough heat from the initial chemical "kick" it may never harden. I had an area like that on my build where I either screwed up the mixture ratio or maybe spread it on too fast and it was too cold to kick. I ended up scraping it down and was glad that I did when I did. While it was still soft-ish it wasn't that hard to remove, and once I was back on track it was business as usual and I kept right on going.
Wasn't that bad just scraping it up.... once I bit the bullet.
When you are pushing close to the manufacturer's recommended working temperatures, one thing you can do to help is once the resin is mixed, let it sit in the cup a little bit before spreading it out. This allows the mass to start to warm up a tad, ensuring that the chemical reaction starts, and the cold temperature buys you a little working time at the other end. In cold weather I always drag my resin and hardener along with me so that it mostly stays at room temperature, then I drag it to the shop for a couple hour session not below 40-45 deg F, then back into the warmth. So long as I feel it start to warm in the cup, even just a little, it works out fine.
My Build: The Poet Creek Express
Poet Creek Or Bust
Engineering the TLAR way - "That Looks About Right"TnTTT ORIGINAL 200A LANTERN CLUB = "The 200A Gang"Green Lantern Corpsmen