So long as you don't wish to claim back the disputed portion, you don't need to do anything. In general if your map shows more than you actually have on the ground it's not really a problem for title. If selling or transferring, just have an engineer mark the map of what you actually have on the ground and sell or transfer this only. Be sure that your selling agent has the map before it is put up for sale and sell based on this map only, not on your title map.
The neighbours will probably have an issue if they tried to sell on as they will have to ask you to transfer that portion to them or do a lengthy and expensive squattors application.