would matter, might matter
Tom actúa como si no importara nada más.
Tom acts as if nothing else matters.
Ella hizo como si no le importara lo que pasó.
She pretended not to care about what happened.
Tom no sabía que a Mary le importara.
Tom didn't know that Mary cared.
No es verdad, si no te importara nada, no te importaría decírmelo.
That's not true, if you didn't care about anything, you wouldn't mind telling me.
— La historia interminable (1984)