Dikgacoi's neck was placed in a brace and he was stretchered off after 67 minutes, before being rushed to hospital with the Palace medical staff concerned over his welfare.
He had earlier scored his fourth goal in just six games for the second-tier side this season, putting his team ahead just after half-time. It followed his goal against Charlton Athletic at the weekend that gave Palace their first win at their London rivals in 44 years.
He headed home a corner five minutes after half-time against Forest and has now more than doubled his career goals tally for the club from the start of the season.
Dikgacoi netted just three times in 44 appearances for the club in his first 18 months with the team, putting into context his excellent return of four in six appearances this campaign.
Meanwhile, Kgosi Ntlhe returned to the Peterborough United starting line-up after he was rested at the weekend.
United suffered their seventh defeat in a row with a 2-1 home loss to Bristol City.
Dean Furman also had another disappointing result in an Oldham Athletic shirt as his side were held to a 1-1 home draw by battlers Scunthorpe United in League One.