What causes cancer soars and how do you get rid of them? Mine is bothering me for a whole week. Underneath there is another but not puffy or yelloe

Need clarification. Do you mean canker sores? Ulcers due to cancer are not an issue for self treatment. For canker sores, check out the site given below: http://www.mayoclinic.org/diseases-conditions/canker-sore/basics/definition/con-20021262.