Leicester remain on track for a crack at a second-successive promotion but Saturday's derby date at Pride Park is the first of three tricky away games in a row.
And after seeing his side throw away a point Pearson admitted that they must now respond with a win against the Rams.
He said: "It's disappointing and I don't think we deserved to lose.
"Over the last two home games we'd obviously expect to get a better return then we have and we need a response now on Saturday.
"But we've done exceptionally well of late so let's not get carried away.
"We had our opportunities in the second-half and it is unfortunate that we have come away with nothing.
"We made their goalkeeper work. I'm not going to start moaning, we are in a good position and we need to make sure that we finish as well as possible."
Jimmy Kebe gave Reading the lead with his seventh goal in 11 games before Martyn Waghorn equalised with a powerful header before the break.
Both sides went close in an open second half before Simon Church went down under a challenge from veteran Nolberto Solano and Sigurdsson rolled in his 14th of the season.
Pearson said: "I've seen the penalty incident and I've spoken to Nobby about it and he felt that he got the ball.
"I've seen them given and seen them not given, it was tight."
Reading boss Brian McDermott insisted that he was not thinking about a remarkable late surge for the play-offs himself.
The Royals were staring at relegation at Christmas but after Sigurdsson's spot-kick made it nine wins from the last 11 they are up to 11th place in the table - just eight points behind sixth-placed Cardiff with a game in hand.
But a cautious McDermott said: "We are not thinking about that at all.
"We were looking down and just hoping to get out of trouble not long ago and to even discuss the play-offs when we were four points adrift in January is testament to how far we have come as a group over the last two months.
"It has been a great run but we are not finished yet."
As the second-half grew on it was the visitors who looked most likely to score again and McDermott felt his side deserved the win.
He said: "You can't beat scoring in the last minute and we've done that a few time this year. From the spot as well.
"I'm really pleased. The commitment was fabulous and the last 20 minutes we were on the front foot.
"We didn't settle for a draw, we went for the win and I'm delighted.
"Two sets of committed players made for an entertaining game and I'm very proud of them. We did what we had to do."