First go to https://scholar.google.com/ and search on Nerve Regeneration progress. This site is for technical papers and searching here will help to eliminate corrupt operators who will advertise anything to you just to get your money.
Next learn how to read these papers. They usually start and end with a summary of the paper. Read the summary at the beginning of many of these papers, within the past few years only. This will give you an idea of the state of the art and what looks promising.