Hello Vicky,
You are a MBA, with both HR and Marketing specialised person. You selected a Marketing job which came your way first. How do you feel in the job? If you are OK with it and have adequate scope for development, I would suggest you to continue in Marketing area itself, even if one or two shifting of organisations are required later for a better position and salary.
But if you are so fond of HR work, which is not very rosy in organisations, contrary to what you have read in text books and cases, you may take a firm decision on it to change and explore the best opportunity for it at the earliest. HR job opportunities are much lesser than marketing jobs. Your 6 months experience in marketing may not be counted as an experience in HR job, unless otherwise you have become a good PR and communication expert.
Good Luck
Dr.Gopan