Well, based on what they tell you current Xrays are very low dose. Radiation exposure is cumulative so 1 Xray is unlikely to do you much harm. If you live in a sunny climate you're likely to have been exposed to far more radiation just from being outside.
As for your little swimmers, they usually shield the genital area from exposure. If you're still concerned, just don't try to conceive until you have ejaculated several times to cleanse your system.