A professor wanted me to wait for his decision. It's been about 10 days, what should I write to show that I want to know how long it is going to take? I am a PhD applicant and a professor interviewed me for joining his team. I waited for his intention regarding my case, after two weeks he emailed me that I should "wait a little bit longer". It's been almost 10 days from his email and about a month after our last interview. How should I write an email to show both that I am still waiting for his response (and interested in his work),and I need to know a timeline for his decision?
*It is already late to get an admission!
It sounds like he's asking you to wait because you're his plan B, not his plan A. In other words, he may be afraid that his favorite candidate backs out, and he's keeping you in the wings just in case that happens. 

So should you push the issue? No, not unless you have other offers. And if your other pending applications haven't been responded to yet, it's in your best interest to wait until those other decisions come back to you.