The veteran centre-back returned to the Blues line-up but was sent off in the 67th minute of their eventual 4-1 FA Cup third-round win over Peterborough United.
Terry went to ground in an attempt to stop Lee Angol but the Posh striker fell as he attempted to leap over the Chelsea great, prompting referee Kevin Friend to brandish a straight red.
Conte said of the decision: "I think the decision wasn't right.
"Firstly, he didn't take the opponent and secondly behind John was (Branislav) Ivanovic to cover.
"It's a pity when this happens. When you get a red card it's not good, you have to respect the referee's decision, but in this case maybe we will appeal because the situation is very clear, John didn't deserve this."