I was always under the impression that a fractured scaphoid gave a deep, dull nagging pain. I am dubious about a ligament strain, just because with the size of the ligament and large movement would be needed to strain it which I think you would remember. But I understand the frustration of not being able to get any further with the x-ray.

Although the main mechanism for a schapoid fracture would be to fall on an outstretched arm, there is also punching and hitting something with the heel of your hand.

I would advise see how your rest and heat go, but if no improvement over the next few weeks then look into it again. Any ligament problem should heal within about 6 weeks, so you should see some improvement.