Indentations are quite natural on radial tires (which most all tires on the road are) and will not affect performance. Your tires feature one or more layers of fabric cord within its sidewall construction that run parallel to each other. (Steel cords are used within the tread.) Where the cords overlap, there is often slight indentation. (For more information on tire construction, click here).
Bulging, however, is not normal on a tire. It notifies that there is a gap between the cords, and must be replaced immediately. Do NOT drive on this tire, even down the road to a tire retailer.
Remember this easy math: indentations = good; bulges = bad.