These bugs are frequently found hanging on a curtain next to my window.
To add to @AL's answer.
This is a beetle of the Dermestidae family. These are a failry diverse group of beetles with a variety of names based on what they are most commonly found eating. Some of the species are specialist eaters of decaying animals. As you have found this one inside it is likely that you have one of the species known as Carpet Beetles. I would go so far as saying that what you have here is a member of the Anthrenus genus. To quote the Colorado Edu site I linked for carpet beetles:
The smallest dermestid beetles found in homes are in the genus Anthrenus. These are typically about 2-3 mm long and have a round body form. Adults have colorful body patterning produced by scales of yellow, browns and white. The larvae are spiny, with a body that is slightly narrower at the head end, which is often tipped with a small tuft of hairs. Species that occur within homes in Colorado, in approximate order, are the varied carpet beetle (Anthrenus verbasci), furniture carpet beetle (Anthrenus flavipes), and common carpet beetle (Anthrenus scrophulariae).
Carpet beetles are common destructive pests eating a wide range of items from clothes (cotton, silk, wool) to dust. If you have these in your house, expect to find holes in some of your less-used clothes, especially if they are stored in dark places.
The larvae are covered in hairs and look like small caterpillars. You may find them crawling along the floor in a quick humping sort of motion, much faster than a caterpillar/inchworm action.
You can control them with regular flysprays, but it is best to get an exerminator in to kill off the infestation and spot-control from there.