Is my earring infected?

It's normal to be sore and swollen for a few days or weeks after getting pierced. Afterall you got a needle pushed through your skin. If you got it done by a pro and you're cleaning it twice a day you should be fine. After a little while you won't be able to tell it's there it might just hurt a bit if you touch it. When it's healed it shouldn't hurt at all. If you get increased pain and green discharge it may be infected but should go away after cleaning it extra well for a couple of days. Sea salt soaks are best (google it) and a drop of pure tea tree oil in the water can also really help if you've got an infection. But its probably not infected now, it's new so it's expected to hurt a bit and be swollen. Sometimes piercings just get irritated too. Infections usually mean an increase of pain and a green/odd discharge (white or yellowish crusties are normal). Just keep the cleaning up and you'll be fine.