Question regarding my right under Section 125 CrPC child maintanance

Our divorce completed in Feb, 2019. Our son resides with his mother.She is having legal custody of her son and I am only having visiting right of my son. His mother is working in Comptroller and Auditor General of India (central government). I work in a PVT company. I was having a job problem in last 6 months and could not sent money for my son maintenance. Now her mother is threatening me to sue me under Section 125 CrPC child maintenance act and Section 26 of Hindu Marriage Act of child maintenance. Her mother is demanding 25% of my salary for child maintenance. Now I have got a PVT job last month. Please let me know what is my legal right in this regard. Am I legally responsible for my son maintenance? For your information, I have been already saving money for my son future education (under graduate and post graduate). And out of love and responsibility, I am ready to send my son a certain amount of money per month. Please help what should I do if she files a case