What To Do To Heal The Cut In The Middle Of My Bottom Lips?

I have a cut (split/slit?) in the middle of my bottom lip. It first split, i guess, about a month ago and although it seems to WANT to heal it still hasn't...Ive put neosporin on it and it didnt seem to help...I just started putting hydrocortisone (sp?) cream on it but I dont know if that's helping either...what should I do??