Current sense resistor - Should I consider self-heating contribution?
Yes, you should account for self-heating using the thermal resistance.
You can estimate the thermal resistance from the derating curve. The max temperature at zero power is the max allowable substrate temperature.

Subtract the rated temperature at full power from the rated temperature at zero power.
125 - 70 = 55 degC
Divide by the rated power.
55 degC / 0.25 W = 220 degC/W
Now, it isn't clear whether this resistor is cooled primarily by conduction or convection. If you assume conduction, then use your local board temperature for the ambient.