If you shot RAW, you may be able to recover about a stop of highlight detail. In Lightroom, first enable the histogram clipping warnings so you can see blown highlights, then reduce Exposure and use Recovery to pull back clipped areas. Apply Recovery carefully, since pushing it too far can make tones look unnatural.

Recovery works best when only one channel is clipped. For flash portraits, that’s often the red channel in skin tones, and Lightroom may recover some detail. But if all channels are fully clipped to pure white, the detail and color information are gone—there’s no true fix. Photoshop retouching or repainting color is possible, but it’s time-consuming and limited.

If the blown area isn’t important, cropping it out can be the cleanest solution.

For future shots, prevent the problem at capture: bouncing flash softens light, but it doesn’t control flash power by itself. Use flash exposure compensation in TTL mode, or lower flash power, ISO, or aperture as needed.