Defender Terry was shown a straight red card by Turkish referee Cuneyt Cakir in the 37th minute for kneeing Alexis Sanchez in the back and will miss the final against either Real Madrid or Bayern Munich on May 19.
"It does look bad on the replay. I raised my knee which in hindsight I shouldn't have done. No complaints from the replay," the Englishman told Sky Sports after his team went through 3-2 on aggregate.
"Sanchez darted in behind me. At the time I was bewildered. I feel like I've let the lads down," added Terry, whose missed penalty cost Chelsea the 2008 title against Manchester United in Moscow.
Chelsea will also be without the suspended Branislav Ivanovic in the Munich final while fellow defender Gary Cahill was injured during Tuesday's match and David Luiz missed the game.
Terry said he was not surprised at Chelsea's stunning upset.
"This is what this football club deserves. It's massive."
Caretaker coach Roberto Di Matteo said: "He's a fantastic leader of this group. Everybody can make a mistake in life. We're just happy to go through. We're all human beings. They're under huge pressure these players."
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