The 22-year-old has not featured since the end of December, but had been on course to shortly complete his rehabilitation.
However, after feeling discomfort during training, an MRI scan highlighted a fresh problem.
Redknapp wants to first see Lennon back terrorising defenders in a Spurs shirt before any talk of representing England at the World Cup.
"Aaron was close to getting fit, but has had a bit of a set-back," said Redknapp.
"He has had a scan, and has just torn a couple fibres apparently.
"It is difficult and has been dragging on a long time. We will just have to wait and see.
"Hopefully it should not put him back much from where he was, and he could still be fit in a couple of weeks."
Redknapp added: "At first the diagnosis was he could be back in four or five weeks, but you never know with these groin problems, they can take time and he has had a couple of setbacks.
"Aaron has worked hard to get fit, but every time seems to have a little problem there.
"Hopefully, though, it will get sorted out and he will be back soon.
"But first and foremost, we have to get him back playing for Tottenham."