[Sacamuelas]

You know, of course, that the safest way to confirm this injury is to get to a local Doc and get an exam/x-ray.

That being said-
Can you extend the finger straight (fully extended) against active resistance? I assume by your above report on ROM that you can close (flex) the finger and open/extend (straighten) the finger when no active resistance is being applied. I am also assuming from your lack of stating it otherwise in your original post that the joint remains stabile during the ROM test.

Is the finger stable laterally when you exam it? Is there any crepitus (grating feeling/sound) when palpated and/or during range of motion functions tested? Is there any specific point tenderness?

If you are thinking it is just a jammed/dislocated finger that you reduced at the initial scene, then you do want to at least rule out a central extensor tendon tear which requires a specific type splinting ( fully extended verses the old standard buddy splint in a slight flexed position) to prevent a permanent "crooked" finger (Boutonniere deformity) after healing if that type injury is present. That is why I ask about the ability to extend the finger under resistance.