No. The nozzles supplied with reloadable propellant grains in a solid rocket motor, or reloadable fuel grains in a hybrid rocket motor should never be modified, since they can result in the destruction of the motor. Modifying the size of a manufactured rocket motor nozzle will subject the rocket motor to pressures it may not have been designed for, and obviously, as soon as it is operating outside of its design parameters, the risk of failure becomes a major issue.