It seems that you are getting distracted by the various suggestions you are receiving. Whatever you have done is already done! Okay! Don't repent for what you have done earlier, as you would have taken up PGDHRM at that moment in time when you had limited understanding of the prospects. 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 with your MBA rather than MSW. I am really not sure if the Institute/University you have mentioned is an approved/recognized one, but any of the other universities, which are State or Central Universities, would suffice. You may pursue this MBA while you are working so that you can continue to earn both money and experience simultaneously. Additionally, your earnings would help you to meet your university course and examination fees too.
Regarding your query, "Should I invest a considerable amount to do an MBA?", I would personally not invest lakhs of rupees to obtain that *expensive* MBA. I would choose an MBA from any State or Central University and strive to excel in that.
I hope this advice helps you make a decision. Wishing you all the best in your career.
Regards,
Suresh.