Seizure... the piston grows in size from excessive heat till the clearance between it and the cylinder bore shrinks to ...... nothing.
The increased friction creates more heat and will quickly start to smear aluminum from the piston on the cylinder bore.
What to do ?
All depends on what exactly happened to yours...
Worst case ?... new cylinder/piston/rings
Best case ?... I have seized motors and let them cool and kept running... no disassembly.
other possibilities ?.. New piston and rings with just a cylinder hone job
Examine all parts
Cylinder ??... any smeared aluminum must be removed.
any heavy scratching and gouging will need boring and honing (unlikely for you... too new)
Piston ??.. really heavy scratching and gouging?.. replace
light scuffing ?.. sand scuffs carefully with wet and dry sandpaper (while wet)
Rings ?? .. If aluminum hasn't been smeared over them... they might be OK (but they're cheap too)