Hello i have found a lump bac of my neck under my hair line its been ther about 4 weeks now my face and head is realy itchy ?

Lump on neck: A lump on the back of the neck could be a cyst or a lipoma. It is unlikely to be a cancer. If you have a rash, with the itchiness, the lump could also be a swollen lymph gland. So i would treat the itchiness with dandruff shampoo and Hydrocortisone cream1%, and i would apply warm compresses to the lump. See a doctor if you are not better after a week or two.