A hanging columella on just one side can result from asymmetric positioning of the medial crura (the portions of the tip cartilages which sit between the nostrils). This can occur naturally or following a prior rhinoplasty, if one cartilage settles in at a different height than the other. Pictures and certainly an in-person examination would be useful to assess your situation.
Correction of this issue can be as straightforward as shaving the lower hanging cartilage, which can be performed through a tiny incision under local anesthesia in the office. However, if there are additional tip concerns, a rhinoplasty focusing on the tip (tip-plasty) may be appropriate. This can be either an open or closed (endonasal) rhinoplasty, depending on the type and severity of issues and the surgeon's preference. I'd recommend seeing a rhinoplasty specialist in your area and ask to see before/afters similar to yours.
Best regards,
Dr. Mehta