I have a ulcer in the bottom part of my lip and ulcers can be from many reasons from hygiene to accidentally biting your cheek or some accident.

I ONLY have ONE and I'm afraid this could lead on genital herpes as there was no protection.
Is it possible to carry genital herpes from one ulcer.

If you were having an oral outbreak when giving oral sex, yes it is possible to pass it on genitally.

It was only one ulcer.. no break out

One ulcer is considered a breakout. It's still an ulcer and is still contagious.

Do you know that you have oral herpes? Is the ulcer on the outside of your lip, or the inside? Have you ever been tested for herpes? You might just have a canker sore or have bitten your lip. It doesn't mean you have herpes.