Welcome to the forum. Thanks for your question.
Just a few days ago I answered a question with a blog-like reply that explains some things about the biology of HIV and STD transmission. Like yours, that question was also about kissing, although my reply discussed transmission risks in general.
http://www.medhelp.org/posts/STDs/Short-lip-tot-lip-kiss--risk-of-syphilis/show/1861534
As for the specific exposure you describe, it's absolutely no risk for HIV. First, it is statistically extremely unlikely your partner had HIV, well under one chance in 1,000. Second, HIV is never transmitted by kissing and rarley if ever by oral sex -- and that includes consideration of billions of sexual events that undoubtedly involved exactly the sequence you describe, genital to hand to mouth and then back to mouth or genitals. Even with entirely unprotected vaginal sex, if your partner had HIV the average risk to you would have been once for ever 2,000 exposures. Given that, and also considering the dilution effect -- the amount of vaginal secretions that would by on your fingers, the amount of that which would get into her mouth, then the amount that would be transferred back to you -- it is simply implausible. I'm sure such a transmission even has never happened.
In other words, there is absolutely no reason to be "very worried about this". You should entirely forget the event. You do not need testing for HIV or any other STD, and if you have a regular partner, you can safely continue unprotected sex without worry of transmissing HIV/STD.
I hope this has helped. Best wishes-- HHH, MD