Jimenez visited the Wolves training ground again on Thursday.
"He's getting better. He will return stronger," said Nuno.
"There's no timetable, no date on that because first of all he has to recover his health and then we think about him returning. But it's positive."
Jimenez scored 27 goals last season and there has been speculation that Wolves will look to bring in a forward in January's transfer window.
"Unfortunately, we had a huge situation that put one of our important players out for some time with a serious situation," said Nuno.
"What happened to Raul is difficult and that's why I'm not happy with the balance of the squad. I think we need to rebalance the squad."