i imported a track from a Tascam PortaStudio, then imported another track from the same source. The starting point of each is slightly different. I want them both to start together to be in sync. I can move a clip easily enough, but can't seem to figure out how to "nudge" the track. I'm running Sonar Platinum. Any ideas?

here is link to documentation that describes this:
http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Arranging.24.html#1470894

If you can visually SEE where the two clips should line up, just drag it over.  Make sure you've got the "snap to grid" turned off.

a Tascam porta studio ?
if its a tape machine the capstan motors run at different speeds through out a song.
even if its + or - 0.2% it will still never line up properly and it will what is called "drift".
I know I do this for side work. I do what is called transfer work.
I transfer old 4 track, 8 track cassette and 2 track, 4 track, 8 track reel 2 reel to digital tracks.
this way you can import the tracks one by one and they line up perfectly.
 
you need an interface that will handle all 8, 4 or 2 tracks at the same time.
don't try recording it separately. you need to record the material all at once.
 
you may be able to find the offending areas and split/nudge them but trust me when I tell you this is one of the most pain staking processes out there. the drift and fluctuations with tape is unforgiving.
 
However, if you want to try lining up the beginning of the material in small tight increments, use the nudge feature by pressing the number pad on your keyboard. not the # on top (under the F1 thru F12) the number pad itself.
1-4-7 nudge it left. 3-6-9 nudge it right.