OS number painted on my property can start construction there

hi, i had bought a property in 2007 after 3 year i saw someone has marked some OS number on my property with black color, ( O.S 5044/2005 ). that time i consulted one of my advocate friend and he said that there is nothing to worry and you can do construction whenever you want. since then i have not followed up this case. now my family wants to build a house on that property hence would like to know the status of the case and whether we can start construction on my plot now. Also what should we do to come out of this. plz help.