I understand your query about whether it is compulsory to file an income tax return when you only have a PAN card issued but no taxable income.
Filing an income tax return essentially means reporting your income and taxes to the Income Tax department every financial year. The purpose of tax returns is for the IT department to keep track of the right amount of taxes paid.
Now, regarding your specific case of having just an income tax PAN card but no actual taxable income, filing a return is not mandatory as per income tax rules. The threshold for paying income tax depends on the tax regime chosen, and only when your total income crosses the minimum threshold does tax payment and filing returns become mandatory.
So, in your case, since you do not have any income that crosses the basic tax exemption limit, you are not required to compulsorily file a tax return. It is fully optional. The only purpose filing a nil return would serve is to inform the IT department that you do not have any taxable income. But even if you do not do so, there are no consequences or penalties.