You should not worry about warm nose of the dog because it does not indicate any pathology. Dogs can get depressed due to many reasons like changes in weather, change of home, new place, new companion, loss of old companion etc. If your dog is also not eating and drinking along with staying in room due to depression then it is not good for him. You and all family members should spend time with your dogs and play with him. This will help to ease the stress. You can also get advice from vet.