Q.meyer lemon
My lemon tree has had 1 lemon on it for about 2 months now and it is all green, 1 inch in size, and it seems not to do anything. I water it regularly, not too much. It is indoors in a sunny place. I fertilized it with egg shells, but still the fruit doesn’t grow. Also, flowers are blooming and make little lemons that fall on the ground. Why? What can I do?

The articles below will help you adjust the growing conditions.
https://www.gardeningknowhow.com/edible/fruits/lemons/lemons-stay-green.htm
https://www.gardeningknowhow.com/edible/fruits/citrus/growing-citrus-trees-indoors.htm