When we measure the temperature of a substance by using a thermometer and waiting until the two come into thermal equilibrium, the thermometer will not display the original temperature of the substance before the thermometer was introduced - the measured temperature will be skewed a little depending on the thermometer's starting temperature. (For this same reason we cannot lower the temperature of a substance to absolute zero by repeated thermal contact with a substance already at absolute zero).

For most practical purposes this tiny inaccuracy due to the thermometer may not be of significance, but I am wondering if it is correct to say that a thermometer cannot actually measure the temperature of a substance?