Yeah, the lump looks big but not ridiculous, and he doesn't look to be in bad condition. My guess would be temperature, given what you've said. If the heat source is out and the daily maximum temperature is 27, dropping significantly overnight, that would very likely cause regurgitation. I'm personally a big fan of heat cords, there are plenty of ways to use them. The tile method is really good. Measuring and understanding temperature should be your preoccupation if you're a reptile keeper, and it's probably the most common problem people have, despite it being the most obvious #1 priority. Back when I was first getting into herps a digital thermometer was about $40+, but these days you can get them for $5 or less, and and infrared thermometer was a few hundred, but now you can pick up a cheap one for about $20, so there's really no excuse or reason not to have them on hand. Even as a kid without much money I invested in good thermometers back when they were really expensive, and they served me well.
Get the temperatures sorted out before worrying about feeding again. Wait at least a few days of having good temperatures, then try offering a feed. Never feed a snake unless you know the temperatures are good, and if you're ever unsure about the temperature being correct, make it your immediate #1 priority. Birds and mammals like humans can thrive in a wide range of temperatures, but reptiles will drop dead or get sick within that range where we or animals like cats and dogs wouldn't even be uncomfortable.