Well there are 3 things you can do.
1. Pull the turtle out of its mouth possibly hurting the rtc.
2. Leave it eat it. And it may be spit out later by the rtc.
3. Keep a eye on it so it doesn't choke.
I guess 3 is a combination of 1 and 2. I have seen pics of rtc eating suction cups and spitting them out.
Mine once ate a rock-like plant fertilizer tab. He was weirdly polygonal until he puked it up. It turned out to be a moot point when a lungfish I stupidly had in the same tank as him bit him in half later that day.