I have a hematoma on roof of my mouth that is sore to the touch. i don't recall any trauma to that area. what could it be? is it dangerous?

Torus: It is possible you have a bony growth in the midline of the roof of your mouth. It is a benign growth. You should be evaluated by an oral surgeon.

Hematoma or bruise?: Hematomas, petechiae , purpura and eccymoses all result from either trauma, infection systemic disease or blood problems (like medicine reactions or neoplastic/cancer changes). Without a clear history of trauma , i recommend you see your dentist to help determine the cause. Lack or presence of pain is not always a good thing.