After having rough/semi dry sex i now have a canker like sore at the opening of my vagina. no itching, but there is stinging if urine touches it.

Check with GYN : Avoid sex for 5 days and if it is injury it will get better.If it is herpetic or infected lesion you need evaluation and treatment. Best to do: contact gynecologist.

Have it evaluated: You need to have an examination as this could be a variety of things from an abrasion to an infection or a sexually transmitted disease. Please have your gynecologist or dermatologist evaluate this.