Tempdb approaching disk max: Is it OK to wait?
This isn't a big deal -- in fact, it's the way a lot of people handle tempdb in the first place:


Add multiple data files
Pre-size files equally to nearly fill tempdb drive 
Set autogrowth to a small increment


If the space you have in there is empty and caused by a rogue report, I wouldn't worry about it, period.

(This does assume you've set up tempdb on a drive by itself, as is generally recommended. If you have other things on the drive that may require the space, you have to decide if there's a risk, and how to handle it).