The day after is REALLY fast ( lice maybe? Phthiriasis or Pediculosis pubis link ) and "tiny bumps"? I don't know if they bite, they probably do under the "right circumstances". In any case lice are annoying but if it's that, your life is not really in danger.Remember, I'm NOT a doctor! (and condoms don't help against lice. Shaving does, if its that!)
Is it possibly just skin irritation?
i doubt the signs show up that fast, I agree with jacquesvol
i know this isn't what you're asking for, but did he have facial hair? my boyfriend does, and I get red/irritated down there and on my chest all the time just from the prickly face.
What STD's symptoms show up a day after?
a guy went down on me, and the next day on the outside of my lady parts is a little red with tiny bumps... what std's show up the day after?