Nipple erection problem

Patient: About two years ago, my nipple had scratches and sore skin during the relationship with my boyfriend. After that incident, I have nipple erection problem. My nipples dont get hard as it used to be. When it gets big, it only stays for few seconds. I think I lost some nerves around the nipples. Many of people said it takes time to recover the nerves. But the incident had passed about two years and the symptoms didnt changed. It is not psychological problem. I took some time to see if it recovers but nothing has changed. Do you think it is possible my nipples to get hard as used to be? Are there any treatments for this?