Hi B.Bach
When I had my teeth (26) extracted I had a post extraction checkup the next day. The dentist took the dentures out, inspected his handiwork in my mouth and put the dentures back in without any problems. On the other hand, I've read on other boards of people taking their dentures out a couple of days or so after extractions and not being able to put them back in. The most common reason for not being able to put them back in was because the gums swelled up larger than the denture could fit back onto.
If you try to take out the denture be careful. You'll probably be able to take them out for a few minutes and then put them back in but that won't give you much relief for long. If you can see that the swelling has gone down quite a bit you should be ok to take the denture out for a while. Start with short durations of time and slowly make them longer. If the denture is still very snug on your gums and you don't want to chance taking them out try lifting them up off the gum a little to relieve the pain. If you have some ambesol or other tooth pain ointment put some on and put the denture back in place. That should help for a few hours.
With the sores beginning to develop you should see your dentist soon to work out those sore spots. Most dentists will see their denture patients right away. If you didn't have a post extraction checkup yet then you should have one fairly soon anyway. In the meantime, rinse often with warm, salty water. It promotes healing and feels soothing on the gums too. If you have any other questions please ask. There are some other new denture wearers here that may be experiencing what you are. Good luck!
Yos