how to solve nonlinear partial differencial equation by using any numerical method please tell me

Personally, I'd say that the simplest thing is to start from an initial guess (even 0) and then compute with one value and one unknown, for example

x * x => x_prev * x

where x_prev is the solution of previous iteration (or initial guess if it's first iteration) and x is the value that you actually compute.

If things goes well, you should converge the the real solution. When the x_prev is same that computed x, you converged.

Another solution is to make a linearisation by Taylor expansion, and then use the previous iteration as working point, from one iteration to anoter, as said above.

Hope it helps