How to sell my own house without our son's permission who don't take care of us from last 6 years?

I am a 66 year old man and my son is a software engineer and he is not taking care of me and my wife from last 6 years. I am a heart patient from last 8 years. He don't talk to us. He is not interested to know about our whereabouts? He even shifted to America and didn't even inform us. We came to know about it after 3 months from some outsider. We don't even have his number. Now to meet our medical expenses and for regular expenses, we want to sell our house and buy a small place and keep rest of money for medical expenses and emergency expenses, but whoever comes to buy house ask us that we should get our son to sign the NOC , then only it is possible to sell our house. I want to know how can I sell my own house to meet my medical and regular expenses without my son's permission. We only get 6500rs as pension.....whatever we got after retiring we used all money to build the our position is very bad. My son told our relatives to see that we don't sell the house......and he even told them that he is allowing us to stay in my own house on his mercy. Please provide legal help how we can use our own hard earned for ourselves without my son's permission.