If I came home late and it is after sunset, should I light the Shabbat candles then?

No. One of the major mitzvot that characterize the Shabbat is the prohibition of all types of work. Lighting a fire is in this category and is strictly forbidden on Shabbat. Once the sun has set, Shabbat has begun and lighting a candle, rather than being an enhancement of the Shabbat, is a grave transgression.

There are some who have the custom of adding an extra Shabbat candle the following Shabbat and thereafter to make up for the shabbat for which candle lighting was missed.