Get some string dude, tie it to the cola, and pull, if your scared (understandably) pull just a little every day, tie the other end to something down low. You can also take the stem, and rub it inbetween your fingers, literally crushing the insides of the stem, hence weakening it, allowing you to pull even further. While this may sound drastic, it really isn't, it's done all the time. The plant will quickly send nutes to the crushed area and heal itself, in fact after it's healed, you'll see a nice big bulge, as if it was swoolen.
You want to try to even out the canopy, so you can get more of that beautiful light to yr plant....this way you'll have HAPPY SMOKING!
Peace
What light r u using, a 400 hps?