It sounds like the engine was "hydro-locked". That is, the cylinder was so full of fuel that the starter couldn't turn it. I doubt you hurt the engine if you stopped using the starter quickly. However, I have seen connecting rods bent by this problem.

When you prime your engine, turn it over one or two revolutions by hand after you prime it to make sure the cylinder isn't full of fuel. NEVER use the starter to prime it. It usually doesn't take much priming to get the engine going. Maybe 3-5 turns with the engine at full throttle and your finger over the carb barrel. With the glow lighter OFF, of course.

Dr.1