"We need to sit down and assess the situation with Watford, because it does not look like an injury that is just going to disappear," said boss Colin Calderwood of the loan signing.
"It could be an extended period out for him. If we play him it could become a chronic problem."
Football League clubs can still make loan signings and Calderwood added: "We have a lot of games coming up and we might need a body.
"With that in mind, we will continue to look. Last season is very much in our minds. We do not want to be short again."
Junior Agogo scored the winning goal at Orient on Saturday and his recent heroics at the Africa Cup of Nations have given him a taste to play at a higher level.
"My aim is to play at the highest level because, as a footballer, everyone's ambition is to play in the top division of whatever country their living in and I'm no different," he told Sky Sports News.
"My main focus at the minute though is to help get Nottingham Forest back into the Championship.
"The people of Nottingham want it so bad. They've been craving promotion for the past couple of years and it hasn't happened yet, but I do believe it will happen this year."