It looks as though something got into the engine on the up-stroke gouging the piston and trapping the ring in the groove. If the ring is broken then rotate it back and forth until it comes free of the piston ring groove. Then take a small Swiss needle file and dress the damaged area of the groove. Then use a wet stone (sharpening stone) if you have one and hand dress the outside of the piston so there are no high spots around the scratch. Clean the engine housing out completely and make sure there is nothing in there, replace the ring with a new one and put it back together. The scratch shouldn't effect your compression. The ring seizing is what did that. IF you can't get one locally you should be able to get a new ring here.

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