Small Stone, Pebble, Stone
noun
You've already learned 石, which means stone. Add a ころ to that, and it becomes a small stone, or pebble.
いしころ
This uses the kun'yomi of 石, which you've already learned, and adds a bit of hiragana, so you should be able to read this!
オレンジ色の石ころが川に入った。
An orange stone entered the river.
このビーチ、石ころがたくさんあるね。
There are a lot of pebbles on this beach.
入り口の前は石ころが多いです。
There are many pebbles in front of the entrance.