In a medium bowl, season the pork with salt and pepper. Add the flour and toss to coat. In a large skillet, heat the olive oil over medium heat. Shaking off any excess flour, add the pork to the skillet and cook, turning once, until browned, about 5 minutes total. Transfer to a platter.
Add the onion to the skillet and cook, stirring, over medium-high heat for 1 minute. Add the chicken broth and blueberries, bring to a boil and cook until reduced by half, about 5 minutes. Stir in the butter and season with salt and pepper. Turn off the heat and return the pork and any juices to the skillet. Divide the pork among 4 plates and spoon the sauce on top.