Terry played for an hour before being replaced by Gary Cahill at Stamford Bridge, with damaged ribs, with a scan yet to reveal the full extent of the injury.
The Blues eventually scrapped through in the absence of Terry, who is hoping the problem isn't too serious.
"I couldn't breathe and my chest was closing up," said Terry.
"I was having a difficult time out there, especially in the first half. Hopefully, I'll be OK. I don't know how long I'll be out. I will have a scan in the morning (Thursday) and we will see where we go from there. It's just horrible.
"When you get one in the ribs, you can't do anything about it, you can't treat it, you just have let it heal, but I can get through games definitely. I thought it was OK but, later in the second half, it just seemed to be getting worse and I was struggling to breathe to be honest.
"It was difficult. I have never felt anything like that before."
Roberto Di Matteo's side faded after Terry's departure, with their Portuguese opponents striking late through Javi Garcia to set up a grandstand finish, before Raul Meireles smashed home, adding to Frank Lampard's penalty.
The win puts Chelsea into the semi-final of the Champions League for the sixth time in nine years, where they face Barcelona, who knocked them out at the same stage three years ago in controversial circumstances.
As if the proposition of facing arguably the world best club team, without Terry the Blues would face a mountainous task of overcoming Pep Guardiola's men.
"It's a very good achievement to reach our sixth semi-final in nine years, but we want to go through to the end," said Terry.
"Clearly, that's going to be tough against Barcelona, but we're playing well.
"I am not sure anyone will fancy playing us at the moment because we are a very good side, especially in this competition. Barcelona are a very good team, but home and away we're a very solid side as well.
"We have shown that away against a very good Benfica side and proved on big nights at Stamford Bridge that we can really upset teams as well. We're confident. It is important we keep this momentum because we're going well in the league. That is the key for us."