With the advancement of fabrication processes, bistable single domain nanomagnets are being exploited to design digital logic circuits. The fabricated circuits are however particularly sensitive to process variations and thermal noise. In this paper we exploit these weaknesses to design a true random number generator. The underlying idea is that the nanomagnet can be forced in a metastable state by using an external magnetic field. The removal of the field will lead the nanomagnet to a random state. To validate the proposed structure we use micromagnetic simulations considering both process variations and thermal noise. We present here our preliminary and very promising results.