I know when a dog's nose is cold she feels good. But what if her nose is hot? It doesn't necessarily mean she feels bad, or sick does it?

it could be a sign that your dog is sick.....
if his nose is still hot/warm over the next few days you might have to bring it to a vet...

but sometimes my dog has a warm nose..and its gone a few hours later or the next day. dont be too worried.

I have never found a hot nose to be a particularly bad sign. It is true that if they are having a bad time their nose is hot but I have found that whe they are perfectly healthy the same thing happens.
I tend to find that our dogs behaviour is a much more reliable sign of something not being right especially if they don't eat normally.