No, you can't (reliably) do what you've done. First off, there is no standard punchdown block (or otherwise), so I am guessing you are using a screw terminal block? That is not rated for CAT5(e), twists are not maintained. You might be able to get away with it for awhile though, but I wouldn't bother.
It's my understanding that by having a lengthy unterminated wire hanging off your network you will introduce problems where the signal will bounce off the end, potentially causing destructive interference, much like the thinnet coax days.
Buy some punch down jacks and a 1ft jumper and simply unplug the end not in use, or better yet pick up a cheap switch. (It's probably just as cheap as the punch down jacks these days...)