Numerical simulations of the nonlinear acoustic waves for medical applications are performed by using Westervelt equation. In this paper, FDTD has been introduced to solve Westervelt equation. Nonlinear propagation scheme is applied on different biological media where a 1 kpa transducer pressure wave of 1 MHz and interactions with tissues are analyzed. Our results show the importance of considering nonlinear interactions in understanding the behavior of sound waves in biological tissues