Suggest Treatment For Discoloured Patch On Face Of Child

I rubbed a small amount of clobetasol propinate cream on my child's face on a patch that I thought was excema. About 3 hours later the surrounding area of his face had become lighter/discolored from the rest of his face. Is this serious/should it come back to more soon? It's been about 12 hours since application and 8 since noticed the color change in his face.