Leroy Sane hit a double to give City a 2-1 Carabao Cup win at West Brom on Wednesday and book a fourth round home tie with Wolves.
But there were initial fears for Gundogan when he limped off following a challenge from Claudio Yacob on his first start since December after recovering from a serious knee injury.
Gundogan will have a scan on his left knee - the opposite one than he injured before - and was clearly in pain but Guardiola expects him back soon.
He said: "I think it's not serious, it's not eight months, but a little injury. Unfortunately the action is tough. He will be back soon hopefully.
"Tomorrow we will make a test. The physio and doctor told me it's not big issue.
"I'll have to review (Yacob's tackle). It's from behind but I don't know if he touched the ball or not.
"I suffer for him. He was on the grass and at that moment you think the wrong situation. You can't imagine, for eight months, to be fighting every day alone."