A force sensor is designed, which consists of a Photonic Crystal (PC) ring resonator integrated on top of a 220nm thick Silicon microcantilever. The quality factor(Q) of the resonator is improved by fine tuning the size of holes inside the hexagonal ring resonator. This force sensor with high Q PC ring resonator is subjected to Finite Element Method (FEM) simulations under various forces below 1microNewton and it is found that Q remains constant for all the forces in the studied range. Since the sensor offers high Q value, it can be used to sense forces in the range of nano Newton. In this work, we have presented the force sensing characteristics of the device in the range of 0 to 1microNewton, 0.2microNewton to 0.3microNewton with increment of 10nN. The force sensitivity of the device is derived as 9.33nN for a wavelength resolution of 0.1nm. The improvement in Q of PC device is explained by using field distribution in the momentum space of the PC.