Compression fittings are funny. Too tight and they leak, too loose and they leak too... Without being there it is tough... but. To put it into words, if when you were tightening it, you didn't tighten it to the point where you thought, "this might NOT be too tight" -- then give it a 1/16 of a turn (tight) and see what happens, if it leaks more, then you had it too tight to start with, if it stops leaking... all is well.
On the opposite side, if when you were installing it you said, "gee, I think that was too tight" -- then you probably went too tight and you'll need a new ferrel (spelling) (the little ring that slides over the pipe)... you'll also want to give the pipe a good working with some emery and clean up and marks, etc. (and at this point, you might as well go another 1/16 of a turn, since you probably went too tight already. hehe.)... it might stop the leak anyway. Like I said, compression fittings are funny buggers.
Hope this helps...