Botched surgery by GP

I went to my GP in the hope of being referred for surgery on the NHS- for gynaecomastia aka man boob surgery. Instead of referring me he told me he could do the surgery in hospital office under a light anaesthetic. He's been my doctor for 20 years so I trusted him and went ahead with it. I wish I hadn't as he caused me the worst pain I have ever felt. He cut around my nipple, lifted it and cut fat out of my chest with a scalpel - under a local anaesthetic. I could pretty much feel everything, I'm not articulate enough to accurately describe just how painful this was. He also left pretty bad scars and left oddly shaped nipples. To make things worse, it had no affect on my appearance so it was all for nothing. I've since had to pay Â?4000 to get this corrected and get my life back on track. I'm now seriously considering taking legal action as I do not think it was right, I feel like I was an experiment and I get so angry when I think about it. Any constructive or relevant advice or insight would be greatly appreciated.