Ct scan done a month ago. it showed a 3mm kidneystone my back stopped hurting 3 days later now i some urethra irritation at the opening it comes and goes ,as far as i know i haven't passed this stone could it be what's causing my tip sting and iriate?

Could be but more likely STD. Get it checked out if exposed.

Your urethra could be irritated from stone fragments. I suggest that you strain all your urine through a white handkerchief and examine for very tiny dark flecks. If you retrieve such fragments bring them to the laboratory with your physician's order for analysis. A urinalysis with microscopic exam could also be performed to see if there are red blood cells present as these are usually prevalent