Your dentist can usually relieve the cause of irritation quite easily. Adjustments after fitting dentures are very common! Until then, a little Ora-base applied to the spot will serve as a bandage if the area is really sore.
If your dentures are old and loose, for your sake, don't try to reline them yourself or use denture adhesives. This can make matters worse, so see your dentist for any denture problem!