One way and pretty easy for a beginner or those with limited PP experience is to copy some of the sky to the right of the blown out area, paste it over the blow out, flip it horizontally, add a layer mask and with a soft brush (color palette to black) slowly begin to brush out the cut edges to blend in with the natural edges of the rest. You may have to resize and rotate to match existing striations (cloud flares) using the "Edit - Transform" menu. You can also lower the opacity of the blend layer and of the brush. I tend to begin with a brush in the 20% range and work up from there as needed. When you are satisfied with the look, flatten the layer.