Sharp had to receive medical treatment after a Forest fan ran at him while he stood on the sidelines following the Blades’ penalty shoot-out defeat.
Thousands of supporters ran onto the pitch at the end of the match and one supporter headbutted Sharp, who is a former Forest player.
Upon seeing the footage, Forest issued a statement in which they condemned the fan and vowed to ‘locate the individual’.
"The Club will work with the authorities to locate the individual in order they are held to account for their actions, which will include a life ban from Nottingham Forest.
"The Club would also like to apologise to Billy personally and to Sheffield United Football Club.”