The wideout told Beisner he is "feeling good" after nursing foot and knee injuries for three weeks.
Nicks, who hasn't played since Week 2, was catching passes from Eli Manning during warmups.
Nicks has 14 catches for 237 yards and one touchdown this season.
UPDATE: Nicks is officially listed as active.
49ers inactives: quarterback Scott Tolzien, wide receiver A.J. Jenkins, running back LaMichael James, safety Trenton Robinson, running back Brandon Jacobs, guard Joe Looney, defensive tackle Ian Williams