If he's having trouble bearing weight on his paw after a nail trim, try some styptic powder... unless she cut off his knuckle, NOT LIKELY, it will be No big deal by the morning.
Amy and the dogs,
Jack - male GSD b. 8/9/10
Lillian - female Weimaraner b. ~2005
RIP Mattie - female GSD 10/18/02 - 7/24/2013