How can i know if this is a cold sore or a canker sore or something else?

Call your dentist: Your dentist can answer that question. He needs to see where the lesion is to determine diagnosis.

See your dentist. : Cankers (recurrent aphthous ulcers) are an "auto-immune" type reaction to trauma/stress (such as biting your lip). They occur on the loose membranes of your lips, cheeks and floor of the mouth. Your dentist can treat with prednisone, laser or chemicals to cut pain. Cold sores are hsv. Abreva helps those some, but most need doc rx. Both go away without treatment in 10-14 days (pain only 3-5 days).