need immediate help!!

My N is contacting me at work (he works there too) via email after i told him i blocked my phone and email and to not contact me again, as of last night. he said someone looked at him funny today so i'm slandering him and am i going to keep doing it? i emailed that it wasn't true, but he only replied that i didnt say i wasnt doing it, calling me psychotic. he wanted an answer and i said i didnt and to please stop contacting me! he said he would go to huma resources to deal with it. no one knows at work, but i was so shake i told my manager, to my great embarrassment. what should i do, i'm at work now!! when i said i wasnt doing it he said ok then have a nice life...i told him again no more contact!!! Someone pls help, im afraid he will keep doing it. Im afraid it will hurt my job and chances of advancement if it gets big but i need it to stop. its a state job, much favoritism and cronyism. called hr and they wont help till i give them his name, then he will be really upset? HELP!!!