How close are you mic’ing from?
I’m guessing you are trying to record an upright.
I have had some success by positioning the mic just above and behind the players head, effectively capturing what the player is hearing.
Getting in close with a single mic is always going to be problematic because a) you will be capturing a narrow part of the sound board and the strings in that region, and b) you capture all the dampers, and what-not.
Of course moving out you will be getting more and more of the room. This is OK if it’s a nice recital room or a properly treated studio live-room, but in the average small domestic space, you are going to record the horrible sound of the room, that our brains are so good at ignoring when we are in the room