The Wales striker equalised within a minute of coming on at Portman Road and Forest went on to secure a 1-1 draw against Roy Keane's strugglers.
Earnshaw was delighted to notch his first goal of the season and urged boss Billy Davies to include him from the start.
"I am disappointed because I don't want to be sat on the bench, I want to be playing football." Earnshaw told the Nottingham Evening Post. "If I am playing football, I am happy, if I am not playing then I am not happy. That is how it is.
"It is good because I was there to help the team, it was nice to get my first goal of the season and get myself started. It gives you a boost to get started. But then scoring goals is what I do, it is what comes naturally to me."