I recently noticed a lump on the shaft but to me now its seems to b gettin smaller and going away what does this mean and what could it be?

Hard to know? So its going away. That is good. However, bad things can go away and leave behind problems. Syphillis can cause a lump (usually and ulcer) and go away but leave behind active disease that can affect you during your life. There are other lump causing venereal diseases that can be problematic. Though you may have a benign lesion, it would be important to have it checked out and diagosis made.
Penile lesion. Get checked by a urologist for a penile lesion...Genital warts, infection, std.