What is the likelihood of getting genital warts if i only had one hpv vaccine at 19 before being sexually active and never finished my vaccination?

The protection provided by one dose likely begins to fade some after a year or two if the second dose is not obtained. Having another dose now could return much of the benefit. Without it your chances increase depending on the HPV status of your sexual contacts. If none are infected, you won't get genital warts, or the more worrisome cancer associated strains.