The odor in your mouth may be the result of many conditions in the oral cavity, throat and/or stomach; oral cancer is one of those possibilities. In your case, it sounds as if an oral infection is causing bleeding, pain and probably the odor. Bad teeth(s), tonsillitis, lack of oral hygiene, and some stomach disorders can cause unpleasant odor. Cancer in the oral cavity can cause an unpleasant odor if it is spread locally and combined with infection. You can use a local antiseptic for the time being and you can visit a dentist soon to investigate other possibilities.