Was this because of the drooping nose preventing it from being placed anywhere further up?
In a conventional "tricycle arrangement", placement of the nose landing gears is normally chosen to respect three basic requirements:
- nose landing gear should carry 10 to 15% of the total weight; a smaller value would imply less authority for steering while a bigger value would imply that the main landing gear is located too aft in respect to CG;
- when braking, an additional load is downloaded on the nose landing gear due to the CG "pivoting" around the braked main landing gear; this has to be limited due to structural reason of the front tires;
- the "overturn" angle $\theta$ as defined in the following picture¹ should be also limited to avoid overturn around sharp corners:
Obviously other non mechanical reasons might limit the landing gears placement but those three requirements should be respected anyway.
Just for comparison, an A321 has main landing gears 7.6m apart and a wheelbase of 16.9m. Concorde had 7.7m and 18.2m respectively, so actually quite a standard placement. Placing the nose gear farther in front would have reduced the weight distribution under the 10% of the previous point 1. and it would have reduced the manoeuvrability on the ground as given in 3.
I don't know the CG excursion of the Concorde, if somebody has a couple of numbers I'd be glad to do the math to show if (hopefully!) the nose gear placement respects those three requirements.
¹ from this paper, in turn from "Currey, N. S., “Aircraft Landing Gear Design: Principles and Practices,” AIAA Education Series"