He's clamped- most likely because of stress, poor water quality, or being cold. He looks healthy, other than being clamped, which isn't a direct sign of illness. However, if he remains stressed or cold for a while, he will get sick. I agree with everything Shadyr said. :) Definitely don't medicate unless you know what's wrong or that there's something wrong.
If he's still clamped (clamped means his fins aren't spread out):
-Make sure the water temperature is between 78 and 84 degrees Fahrenheit.
-Make sure he has places to hide. If you're in a bind for something for him to hide in, rinse out a glazed porcelain coffee or tea mug very well with very warm/hot water (no soap, the idea is to remove any residual soap) and put that in there so he can hide in it. You can also turn out the light so he's more relaxed.
-Depending on size of tank/whether or not you have a filter/live plants, make sure you're doing enough water changes. If you need specifics about how often you should, reply back with that information and we can give you an estimate.
-If you have a filter, make sure the current isn't strong. He should be able to swim effortlessly without being jostled by it. To reduce filter current in my waterfall filter, I rubberband Fluval (or some other brand) filter sponge around the filter outtake, but it depends what kind of filter you have. This is what I mean:
I got Mr. Fish from Wal-Mart and he was in pretty bad shape (he'd been in a fight and lost most of his fins), but he lived a good life! He looked a lot like your new betta after his fins grew back.