My neighbor is saying that my water well that i drilled is on his land?

ok when i bought my land and house in 2005 the company i bought from had the well septic slab everything. it was all brand new they had a surveyor come out prior to doing anything to the land so they did all the work now 6 months ago someone bought the land next to me he asked if he could use my well i said if he made up a contract saying he would pay every month he said he would pay 30 dollars to use it so he taped in everything was fine till he wanted to put up a fence and had a surveyor come out he was told thad the well is on his property and the first surveyor did it wrong so he stopped paying now he is taking me to court hat should i do