How risky is Revision Rhinoplasty?

I had a first op in 2008, but was left with a very asymmetric tip and prominent columellar show. I decided to have a small revision in Dec. 2014, under local anesthesia. The dr used cartilage from the tip to correct my V deformity and also rasped the bridge, but now I have a callus formation which still shows after 11 months, a columella that's still too big and the tip seems to have sunk. How risky would be to undergo a new surgery for rasping the callus and lifting the columella a bit more?