swollen lymphs

well i have a question about lymph nodes. i dont know if it is lymph nodes or not since i searched on the net it says many different things. under my armpit i began to get tiny bumps. but not all at once. one will apear and go away and another one will apear and go away. they are as wide as a pencil eraser at the most. the dont hurt but i do feel them and they are a pinkish color almost red, u can see em a little but they dont get swollen or come out the skin as much. kinda like an ingrown hair or clogged up pimple. my question is, how are swollen nodes. are they visable, can u feel them? do they hurt. i also have a question about hiv exposure. i heard that its hard for a woman who has hiv to transmit it to the male. well the odds are low? is that true? especially if it was a one time thing. like u only had sex once. is this true?