Neighbor built boundary wall on my plot land

I need one help or suggestion. My father retired 7year back based in Kanpur UP. Till now we are living on rent. Now my parents decided to construct a Home roof for us over pre-owned land from KDA. In my words of taking all financial liability with me. Started construction work this month, during measuring and base pit digging, found that neighbor has built his DPC boundary, 6inchs inside our land.. Neighbor came with few people to my parent and cold intimidated, "boundary mat touch karna wrna accha ni hoga, jo karna hai ja ke complain karo. Bujurg ho samjhdar ho issliye baat kar rahe hai" and introduce himself as a Lawyer and 2nd person as some leader 3rd as some business contractor.... My parents step back and said, "6inches se kya jayega, itne saal baad ghar bana rahe hai koi tension nahi lene, construction ruk jayega". hence koi action nahi lena. Our priority is to complete the house, what can we do or what are our rights for this? without getting involved in any long-run dispute or court case.