You need to counter the same in form of counter action and contest the same in respective courts if any case is filed against you

prior permission from collector was necessary to purchase agricultural land belonging to scheduled caste / tribe 

2) your transfer can be declared null and void and possession restored to harijan 

He has no locus standi to file suit or challenge your title. His case liable to be dismiss with cost. Frivolous litigation.

The land was purchased from a sc person without involving govt. Authorities as was mandated in the zamindari abolition and land reforms act. This bar has now been removed.

Therefore it can be cancelled. Kindly tell us what is the stand of the seller.

Regards 

Yes there is a restriction on transfer of the land from Harijan to any upper caste person if you have not taken the permission from the sub-divisional magistrate in this regard your registration is subject to cancellation even if there is a problem from the government department that they ignored the situation that the land belongs to Harijan and allowed the registration eventually you will be the only sufferer in this case

Section 42 (SC, ST Act) provides some general

restrictions on sale, gift and bequest of the

interest of Scheduled Caste and Scheduled Tribe,

in the whole or part of their holding.

a scheduled tribe land holder can only sell his

land to schedule tribe person. if you buy a land

from a scheduled tribe by hiding facts, you can

end up in jail time, and government will return

back the land to original land owner at anytime if

he approaches authority.

If it was not an allotted land to the said person who sold this property then there may not be any problem in this regard.

If a neighbor is creating problems on this, let him do it, you can face the authorities as per law or you can file a declaratory suit before a civil court to declare the title if you have purchased the land by a registered sale deed.