It is submersible pump

Does it trip immediately or a second after the pump kicks on? Before I pulled the pump to check the motor windings first replace the breaker. If it still blows then I would suspect a short in the power lines or shorted motor windings. Good luck, Tom

I think you should tell us a little more about what's going on.

First thing would be to disconnect the wiring at the well head in an attempt to isolate the problem. If the breaker no linger trips after you have disconnected the wiring at the well head, that would indicate a problem with the pump or a problem with the wiring going down the well to the pump.
If the breaker continues to trip after you disconnect the wiring at the well head that would indicate a problem with the wiring between the breaker and the well head.