I dropped "something" down my intake once! Didn't know until I fired up and heard the tapping. I poured tranny fluid down the carb while it was running and it seemed to had cured the problem.
Later, I took the head off anyway and the one piston had a couple of minor scratches. I didn't do anything further. Got off lucky.
..and sometimes, not so lucky........ Many many years ago, I was changing my points and dropped the tiny screw into the distributor. I could see it but not reach it with sausage fingers so I gave the ignition a short click to move the distributor to create a bigger opening. Got it! ..... but, after attempting to start the engine, the distributor spun freely. That "short click" cracked the slot off the distributor shaft.... Doh! (I should have yanked the distributor out and simply dumped out the screw )