Welcome K3bzr18 and your mischievous conure pair!
I'm not sure whether you should expect another egg here or not, as green cheeks generally tend to lay eggs at around 24 hour intervals and it would appear to now be longer than that since that first egg appeared. Keep a very close eye on your hen to ensure she does not appear to be labouring to breathe or obviously straining to lay another egg, as this can indicate she may be egg-bound which is very dangerous, and you'll need to contact an avian vet ASAP if she does this. Usually where one egg has appeared another will be on the way, although this is not always the case.
Is this the first egg she has ever laid? Sometimes first time egg-layers just don't recognise the egg for what it is and don't take a great deal of interest. Having said that, green cheeks are a species that often don't show a lot of interest in the first few eggs until they've laid a whole clutch of 4 or 5 eggs. With luck, it might just be a once off and she might not lay any more, but obviously it's not possible to say which might be the situation with your hen.
Captive birds can and do breed outside the usual breeding seasons in the wild so this scenario may crop up for you again in future. If they are currently caged together, you can investigate caging them separately, obviously with the cages side by side and allowing plenty of well supervised out-of-cage time during the day so they don't get stressed. I once had a male and female cockatiel who were SO crazy about each other that I'd have been up to my neck in babies in no time flat if they hadn't had separate cages. They actually spent a lot of time out of their cages, they were loose whenever anyone was home, so in their case they really suffered no stress in being caged separately at night or when we were away from home. Individual results will vary with this of course, I can only hope that yours will be as easy to manage as mine were if you do separate them.
I wish you all the very best of luck with your little pair