A MBBS degree is a valid graduation and can be used to pursue any career as one wishes. I know one of my friends who had an MS degree from AIIMS and was working with CGHS in Delhi. He left the profession and joined IAS services in 1985, becoming a very successful administrator. A doctor with an HR degree can have a bright future in the HR field as they have in-depth knowledge of the medical profession apart from HR.
Nowadays, the medical profession is a corporate business, and all good hospitals are managed professionally. Normally, an HR person may find it somewhat difficult to understand the special requirements of medical/hospital staff. In most hospitals, I have seen doctors handling HR jobs, and many of them lack information about HR and other related legal matters. I am sure a doctor with an HR background will have a far better understanding of the needs of the hospital, in addition to understanding the aspirations of doctors and other paramedical staff.
These days, management degrees in the medical profession have become quite common, and many doctors are pursuing these degrees. So, please don't worry. If you have an interest in HR, you should pursue it. I am confident that an HR degree, along with an MBBS, will be a valuable qualification to secure a good job in any reputable hospital.
Best wishes.