I can tell you are panicking, but there is really no risk here.
If the head of your penis didn't go in her mouth, there's no risk for anything that resides in the throat.
Syphilis, which can be anywhere in the mouth, wouldn't transmit so quickly. Herpes type 1, which isn't bacterial, but viral, wouldn't, either.
A few seconds of a lick isn't going to transmit an STD.
You are fine, and do not need to test.