What action can be taken if hostel allotments are not out just after admissions are done?
There are two things you need to do:


Apologize to the Dean of Student Welfare for the unauthorized stay in the hostel, explaining that you thought you had permission.
Find somewhere to stay. Possible resources include hotels, AirBnB, the university's housing department, the Dean of Student Welfare (after or as part of step 1), and personal contacts in your department.