You should avoid oral sex when you have active cold sores. You could transmit HSV-1 genitally to your partner, even though taking the Valtrex probably reduces this somewhat. I highly doubt you could acquire genital HSV-1 from this exposure. Since you have HSV-1 orally, you are pretty much immune to getting it genitally and it is unlikely in the manner you describe anyway. Hope this helps.
Best,
Em