Child Visit/Custody

My wife left home with my child of 2 years in year 2011 and filed 498 and domestic violence cases against me.I got divorce in June 2018 on cruelty basis as her charges were found to be untrue.My ex wife died on Dec 2018, and my in laws didn’t want to handover my child. I didn’t object since he was staying with them and uprooting him soon after his mother’s death didn’t feel right. Then I travel out side country for 2 years and in between then didn’t let me talk to my son. Now I have opportunity to include my sons name in my PR application for Germany, but this required my son’s medical exam and passport. But my in laws are not listening to anything and refuses to talk. This will hamper the child’s opportunity if in he becomes adult and want to study/find opportunity in Europe as I will loose the chance to sponsorship my son later. I need to submit his medical as I am filing for immigration and need to submit in 30 days. If I file for custody in court it will take long time and I will not be able to submit my son details for immigration. What are my speedy legal options to get my son medical done ?