I feel like I am holding a grudge.
Why are you holding a grudge?
Because I've been humiliated by someone for a long time.
Being angry with someone who has made your life more difficult is understandable. Just make sure that grudge isn't damaging your friends or family around you.
I've stopped talking to him and my grudge is healthy.
It is normal to be angry with other people sometimes. IF you think it is becoming an obsession you should talk to a professional about it. It can be really unhealthy to not move on.