Tomori struck to give Chelsea a 2-0 lead, but the Tigers made it a nervy finish with a late goal.
The defender stated afterwards, "We could have killed the game in the first half.
"We said at half-time that we need to be solid at the back. My goal came at a good time but it got difficult at the end.
"It is a one-off game and teams will go for it. If we got the third it is easy but we had to ride it out."