What can I do if my land is occupied by some one?

My uncle requested us to allow him to use my store room, we gave the duplicate key to him in 1984 and since then he has just used it as a store room along with us.We are the legal owners and pay all taxes from 1984 to today. He never paid any rent based on a humanitarian basis we allowed him. Uncle expired in 2000 and later his wife(my aunt) used it as a store room along with us. No one resided there. In 2020 covid time aunt did some cleaning and kept some old clothes/vessels for the first time. We thought maybe she did it in a good way but she never resided there that store room is not in a condition to live in also as it is 80yrs old which is about to fall. She was on good terms with us but in Feb 2023 we asked her to vacate but she refused. We filed a complaint with local police but they raised NCR(non-cognizable) during enquiry aunt for the first time showed an unregistered sale agreement of the year 1995. Police said it civil but its illegal trespass Can we file FIR in this case?