You should have taken legal action at that time itself when the neighbor started constructing the proeprty at the backside of your house especially when he had occupied your space and has constructed his house without giving setback space.
You can file a mandatory injunction suit seeking to remove the structure he has built which obstructs the air and light to your house.
Easements are legal designations that allow individuals or entities to use portions of your property (to build on or for physical access), even though you still own the land and technically have a right to build on it.
Easements in Gross are easements that grant the right to cross over someone else's property to a specific individual or entity and, as such, are personal in nature. In other words, they do not transfer to a subsequent owner.
An easement is a privilege, without which the owner of one tenement has a right to enjoy in respect of that tenement in or over the tenement of another person, by reason where of the latter is obliged to suffer or refrain from doing something on his own tenement for the advantage of the former.
The extent of a prescriptive right to the passage of light and air though a certain window is provided for by s. 28(c) of the Indian Easements Act. An easement of light to a window only gives a right to have buildings that obstruct it removed so as to allow the access of sufficient light to the window
Thus you can file a suit for mandatory injunction seeking easement rights on the above lines.