There's plenty to do, if you want to! I'm sure some Chilean members on here will give you more detailed info, but, off the top of my head, some of the things to to are 1: take the funicular up to Cerro San Cristobal for a terrific view of the city, or 2: take a wine tour. or 3: stroll around the Bellavista area for cafés and restaurants, and 4: check out the Mercado Central, again for more places to eat. And you have to try the collectivos for getting around the city!
And, if you're there for a week, you can always get away from the city for a day or two by going to nearby Valparaiso (which is a real treat) and the resort of Vina del Mar.
Here's a link with some basic information: