Nothing to worry.
Lump on the side of your head may be due to some Cystic swelling,probably Sebaceous cyst.It originates from hair follicle.As it contains white,fatty,semisolid material it will be soft.If it gets infected,it will become painful.
Another possibility is a Dermoid cyst
which occurs at the fusion of suture lines in the skull.
Soft swellings like Lipoma(swelling of fat cells),Haemangioma(swelling of blood vessels) have to be excluded too.
Please consult your surgeon and get it treated.
Wish you good health