Hi Ravi....
First of all login into this PC with Admin.
Then go to C:\Program Files (x86)\SAP\SAP Business One
and Copy AddOnsLocalRegistration file and save it in one of the local drive
Then Open AddOnsLocalRegistration file from C:\Program Files (x86)\SAP\SAP Business One path and delete all the texts inside and then save it and then try to login in SAP with admin rights.
Hopefully your issue will be solved....
Regards,
Rahul