Hello Nilima,
It looks that you are getting distracted by the various suggestions you are getting.
Whatever you have done is already done ! ok !!! Don't repent for what you have done earlier, as you would have taken up PGDHRM at that moment of time, when you had limited understanding of the prospects and while going through the course you would have come across the fact about being a Post Graduate (i mean, MBA or MSW). No worries.. this happens to many of us.
Now, a wise decision would be to continue your MBA than MSW. I am really not sure if the Institute/University you have mentioned is an approved / recongnized one, but any of the other universities which are State or Central Universities would do. You may take this MBA while you are working, so that you can keep earning, both Money and Experience at the same time. Also your earnings would help you to meet your university course and examination fees too.
For your query, "should i invest considerable amount to do MBA?", i would personally not invest Lakhs of rupees to get that *expensive* MBA. I would choose any State or Central University's MBA and try to excel in that.
I hope this helps you to take a decision.
Wishing you all the best in your career.
Suresh.