With a hot runner, the piston and cylinder become so hot (expand) that the piston and cylinder wall 'damage' each other.
The piston damages the wall of the cylinder, which can even result in blockage of the rear wheel (quite serious: a hot runner can only result in less force / loss)
It is advisable to check your citta, to see what the damage is. The cause of the heat runner is the cooling, which is often caused by the wind and the petrol mixture. Is your carburetor well adjusted? if it is too poor, this also results in poor cooling. Was it by chance very hot?
A jammer has more disastrous consequences, a hot runner can cause the piston to jam in the cylinder wall, but a jam can also occur due to, for example, poor crankshaft bearings or other mechanical defects.