If i have an open sore in my mouth and i chew, will it increase my chances of oral cancer?

If tobacco, yes: If by chew you mean by chew tobacco, you have an increased risk of oral cancer. You need to have the "open sore" checked out asap to make sure it is not cancer.

No: Adults over 18 are at risk for oral cancers. Risk factors that increase the chances of oral cancer are alcohol and tobacco use, especially together. Eating when you have an open sore may hurt, but won't increases the chances of developing oral cancer.