I agree with the last two posts. It is definitely normal for your labia to be swollen when you get aroused... but if it continues and is painful afterwards he may be too rough on you or you might just need a little bit more lube.
It is normal. Mine gets swollen every time my husband and I have intercourse. If he does any fingering or clitoral stimulation that could cause it also. A lot of blood get's to that area because of you being sexually stimulated. It could be also if you had a little rougher sex, and didn't have the lubrication. If it gets really painful than I would have a doctor look at it or give you some advice.
It is normal for the lips to get a bit swollen as part of the many reactions of the body to being sexually excited. If they are seriously swollen, and/or are sore (genuinely painful, not just super-sensitive which is normal), then there may be some problem there.