I agree with Dr. Morrisette that the addition of a chin implant would be advisable. A second genioplasty can present many potential complications such as nerve damage fractures of the chin and dificulty with the procedure its self. Best wishes
To fix the cosmetic problem of a chin dimple, either a chin implant or the use of fillers would give you the correction you want. You must find an expert facial plastic surgeon to help you with this. I hope this helps.
Sometimes genioplasty like rhinoplasty takes more time to appreciate the final results. An advancement of 6mm is normal. I think that your chin "fits" your face and looks good. I would allow more time before suggesting any changes. It is possible to diminish the amount of pointedness by shaving...