I think it would be nice if you had one from your master's program, but considering it's not a SMP, it probably wouldn't matter. That said, how do you know it won't be a solid letter?
I was in your position when I started. You really should get LORs from your current program, especially professors you work with and hook up with the school‘s health professions office. You need to show the medical schools that you are past what happened with your academics in your UG years and that you can handle the rigor of the academia in medical school
