I think you diagnosed the cause correctly, the left hip being lower than the right due to road curvature. Probably a strain in the IT band that wraps around the hip down the outside of the thigh then into the knee. You have tried some rest, try also specific stretching (various yoga positions help), use a foam roller or a "Stick" to self massage, and ice. Do this several times a day. One take-away from your experience is to be aware of road crowns and either balance running on both sides of the street or in some cases, down the middle. Ok, two lessons: when something hurts, stop. This is different than sore, pain is no gain. Take care and good luck.

BT

IT Band injuries are incredibly common and can be incredibly painful. The tough part is that they can manifest themselves in so many ways - pretending to be knee, hip, or muscular injuries.  I'd second the suggestion for a foam roller - I love mine, even if it hurts. A lot. When I was training for my marathon last fall, I was using that thing at least twice a day.  I use it on my back (vertically and horizontally) and on the side of my leg, rolling all the way from hip to knee.

If you have any setbacks, see a doctor and make sure there isn't something really wrong.  Good luck - you should be fine in time for your race.

As has already been recommended, I would certainly look into your IT band ( use http://www.bulletproofknee.com ), but I would also look into your hip flexor flexibility. If you have tight psoas, hip flexors, you tend to over use the external hip rotators and can get pain that feels like "hip socket" pain...