What obeys ohms law nichrome thermistor or diode?

Ohm's Law only applies when the ratio of voltage to current is constant for variations in voltage. If you were to plot a graph of current against voltage, and the result is a straight line, then Ohm's Law applies; if the result is a curved line, then Ohm's Law does NOT apply.

Ohm's Law is NOT a universal law; in fact, if barely qualifies as a 'law' at all because, in most cases, it does not work!

Nichrome alloy is designed to retain a constant resistance over a wide range of temperatures. So it is considered to be 'ohmic' or 'linear' because, when plotting current against voltage, it produces a straight-line graph, for variations in voltage. So, nichrome obeys Ohm's Law.

Thermistors and diodes produce curved graph lines and, so, are considered to be 'non-linear' or 'non-ohmic', and do NOT obey Ohm's Law.