I have a small white bump below lashes on upper eye lid for 6 mons and treated still there could this be cystic basal cell ca ?

Cyst: Could be a milia, hydrocystoma, or other benign growths vs basal cell. See a derm who may be able to tell without removing it.

Yes: I am not sure what you mean by "treated" but i would definitely get a biopsy if it has been there for six months. It is most likely a benign lesion, but basal cell carcinoma is increasing in incidence and a biopsy is very easy for an eye surgeon (ophthalmologist) to perform.