Road debris got kicked up into it perhaps. It does look to have a definite dent/sharp impact where the oil is coming from. Maybe a nail or ??? spiked it, but that would take a LOT of velocity for a nail to make a sharp crease like that.
Oh ... been on any limestone driveways, lots, roads etc?
Limestone or other stones can have pointy ends to them & they have the weight that can make a dent like that. Pinched up from the inside edge of a tire & voila!

I've seen rocks being pinched from the outside of a tire fly clear across a 30' ditch. Pretty sure we all can relate to that.