small painless bumps on penis shaft under skin

Hello, Welcome to the forum and thanks for posting on it. Without examination it is very is very difficult to precisely make a diagnosis but two important possibilities n your case are pearly penile papules and Fordyce spots. Both of these are normal variants on the penis and are harmless. Pearly penile papules are multiple in number, small (about 1-3mm) domelike papules arranged in a row of multiple-grouped lesions along the corona and sulcus of the glans and head of penis. They typically develop in men aged 20 to 40, and presentation may occur in males in their second to fifth decades. Ablation using carbon dioxide laser, electrodesiccation with curettage, cryotherapy and excisional surgery have successfully treated them. Fordyce spots are small, painless, raised, bumps 1 to 3 mm in diameter that may appear on the penis. They are also non-infectious and a natural occurrence on the body. The other possibilities for such small bumps can be lichen nitidus(1-2 mm, discrete and uniform, shiny, flat-topped, pale flesh-colored or reddish-brown papules), lichen planus( papules with smooth or fine scales and arranged in a ring), small cysts, angiokeratomas(purple spots with a thick, warty surface) or genital warts( presents as either small painless, flesh colored bumps or brownish, cauliflower like growths). I suggest you to consult a dermatologist and get the diagnosis confirmed. I hope it helps. Take care and please do keep us posted in case you have any additional doubts. Kind regards. You can find relevant information about this on the following site: http://www.skinsight.com/searchResults/adult_Male_Anogenital.htm