I have a sore on the wall of my mouth nd it hurts when i eat, what is it nd how do i get rid of it?

Should be evaluated: There are many possibilities. Diagnosis would need examination (eg ulcer vs lump vs cut, bleeding vs not), also obtaining full history of the symptom (eg. How long it has been there, what seems to make it worse/better, other questions), other history (eg. Tobacco use?), possibly tests/cultures of it. Infection, ulcer, laceration, cancer (esp in tobacco chewers), oddities (behcet's disease), more.

Mouth sores: Mouth sores are painful. Most disappear by themselves in few days otherwise go to dr. Unless rare causes (lupus or syphilis or cancer, treatment is symptomatic. You may try mouthwashes with antacids in liquid form like maalox with liquid benadryl( diphenhydramine). Your dr. May prescribe xylocaine (lidocaine) in gel for mucosas to anesthetize the area or get oragel. Let dr or dentist take a look at that.