Hey, @Athrava Gulve,
Which version of Python your Pycharm is set and on which version of Python you installed the module, please post the versions here. You can do more things, Go to File -> Settings -> Project:.. -> Project Interpreter, and check which version of Python you run on the project. Then go to the CMD/ terminal and write pip -V and it will tell you the pip version and the Python one. Might be a different version.
At a guess - installing the correct library into your environment would help.
I don’t know if you are using a virtual environment - they certainly recommend, but in your working environment (i.e. the same environment you are trying to run the script) execute this command :
pip install pyttsx3
I think you are missing the pyttsx3 package.