Forest boss Colin Calderwood told the club's website: "It's disappointing because we need all hands to the pump.
"Nathan tends to go on goalscoring runs and we had hoped the goal against Swindon would be the first of many."
Injury setback for Tyson
Forest boss Colin Calderwood told the club's website: "It's disappointing because we need all hands to the pump.
"Nathan tends to go on goalscoring runs and we had hoped the goal against Swindon would be the first of many."