My finger got najis by touching essential najasat, then I remove the essential najasat and washed my finger thrice so finger become paak right? But the thing was that I has some oil type grease thing under my nails and some near my nail on skin. I tried to remove that but it was hardly coming out because it was under the nail. So that thing was under my nail before my finger got najis, and after the procedure of making paak also, its there. So my finger is paak now?

If after washing the any part of body the original Najasat has been removed and has no najis particles on it, then the surface of body will become Pak.