Heat the engine cylinder. This will loosen your piston. (when hot, the liner expands more than the piston)
If your mixture is too rich, the oil is thinned. because of the piston pinch in a new engine, this will stick the piston in top dead center. This is normal.
Use more oil for running in, and do not flood the engine. Heating the engine before starting also helps.
A tight piston is the sign of a good engine. You should respect it. The engine will give better power, and last longer.