Nkunku joined Chelsea from RB Leipzig for £52m this summer but will miss the start of the season and is out for an unspecified period after suffering a knee injury in a warm up game against Borussia Dortmund last week.
The 25-year-old France international scored three goals in five games during pre-season.
With Romelu Lukaku still out of the picture at Stamford Bridge, Chelsea only have summer signing Nicolas Jackson and Armando Broja as recognised centre forwards.
As a result, the club are already in the transfer market to find a solution to their attacking shortfalls.
"We are working in the market because we are going to miss an offensive player like this," said Pochettino.
"The club is working, trying to find a solution for maybe short term, medium and long term to add the right profile for the team to perform from now."
"We feel very sorry about him. He was doing well, he is very important for us," Pochettino said.
"Now it's about not thinking too much about the injuries and to be positive about when he can be back with us."
Chelsea start their 2023/2024 Premier League season at home to Liverpool on Sunday.
