How are you? Aside from the lump, what other symptoms are present? If there was no history of head trauma, this could be due to benign lesions, mass or cysts. Scalp cysts, in particular may look and feel like a pimple and typically occur when a hair follicle in the scalp becomes infected. This may also bleed and leak keratin, which is a whitish-colored fluid. Most of the time scalp cysts go away but may become very large. Try not to scratch to prevent secondary bacterial infection. If it persists, it is best that you have this checked by your doctor for proper evaluation. Direct clinical examination as well as additional diagnostic tests like neurological exam and imaging studies may be indicated. Take care and do keep us posted.
From your symptoms, one possibility is of an infected and inflamed cyst like a pilar cyst. It is a benign cyst on the head and neck which is mostly painless but can become painful when infected. Treatment includes topical and oral antibiotics and surgical incision and drainage.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.