Ouch! How did you remove this? Ideally, it's not supposed to come out that way.
A
balljoint press tool should work. Even a gear puller, at this point, since you now have such free access with the steering knuckle "out of the way".
Or even, seeing that your dust boot is torn, a pickle fork (might need to grab the extended part in something fixed/massive, like a bench vice) should do the job. Given you'll be replacing this rear tie-rod part, marring its threads in vice jaws (and for that matter, further tearing up that dust boot) should not be an issue. You'll want to save that knurled steel part, though, as it needs to be pressed back into the steering knuckle and re-used, as I believe you already know.
When pressing the knurled steel part back into the aluminum steering knuckle, it's a perfect application for permanent strength threadlocking fluid (e.g., loctitie 271/272). Be sure to clean, very thoroughly on both the male and female surfaces, first. Best of luck!