What does it mean after sex out lips of vagina a little swallon and a bit sore.goes away in a couple of days?

Normal: Lubrication may help.

Normal: It can be normal swelling from impact, particularly depending on exactly how "parts match up." as long as resolves spontaneously, should not be a problem.

Trauma?: Are you having aggressive sex with some trauma to your pelvis? Are you using a vaginal cream or is your partner using something to which you may be reacting? If none of these seems to fit, you may want to be examined by a gynecologist when it occurs next.