Hello and welcome. So sorry to hear of what you've been going through.
Nerves take a long time to heal. Has your doctor put you on any medication? There are some on the market that can help somewhat with nerve pain.
Are you in physical therapy? Back in 1996, when my ulnar nerve transposition was done, my P.T. used a modality he called 'points'. A stylus would be placed at certain points along the nerve path and an electrical charge would be sent through the stylus. It was quite similar to the electrical jolts that were happening on their own but somehow seemed to calm the nerve down.
My nerve wasn't 'nicked' or 'severed'...it was shredded. It was 5 months before the damage was 'discovered'. I had a 3/4 thickness tear of the rotator cuff that had to be dealt with first. Not realizing that the sheath had been split open and the nerve was rubbing back and forth over the bone for those months left me with only about 20% of nerve function. With a lot of work and diligence, I have regained the majority of function in the pinky and ring finger.
Massaging along the nerve path, while painful to do, will actually help desensitize the nerve. I found heat helped more than ice, but everyone is different. Try one, than the other and see which gives you the most relief.
multiple surgeries for rotator cuff both shoulders with residual chronic impingement syndrome, ulnar nerve transposition, carpal tunnel release, wrist ganglionectomies/denervectomies/tenolysis, multiple herniated discs, tarlov cyst, whiplash, bursitis of hips, tendonitis, torus, 3rd degree shoulder separation, torn labrum, ovarian cysts, fibroid tumors of the uterus