erm it's called a yellow head WASH it
I find I sometimes sweat even on my penis by masturbating and that means also emmision of stuff that needs washing off it is as simple as that, and of course make sure you squeeze it well.
in case your wondering yes it happened to me too but I did not need to interogate the encyclopedia to get the answer.
hope this helps you out

Most guys have probably had them a few times in their lives. Nothing that a little more specific hygene shouldn't take care of.

Have you been sexually active with other people? It's possible you caught an HPV (genital warts) infection. Certain strains look like pimples.

You can be infected for years and have not symptoms. Also you can transmit HPV if you have no symptoms.

[quote=http://members.optusnet.com.au/austbua/penis.htm]I have very small pimples on the under side of my penis as well as the base of my penis. They fade away and then another or 2 can come in. They don't itch and when I pop them they just bleed a little. Is this normal? (35)
It's impossible to tell what these are without an examination. There are some really benign conditions such as "pearly penile papules" these are normal growths that appear around the hair follicles, or an infection of the sebaceous glands can cause pimple like growths. These can be simply treated using antibiotics.

The check-ups for guys are really simple. Go to your local Sexual Health service or make an appointment to see your own doctor. This is the only way you'll know for sure. (35)

I am 16 and have got lots of little white lumps on the underneath of my penis. They are not sore or irritable and I have not had sex. What could it be? (34)
The little white lumps you mention on the underside of the penis are almost certainly normal. Often seen in the teenage years, small pimple-like glands, about 1 or 2mm diameter, can be seen underneath the foreskin. Sometimes known as 'Fordyce's spots' they are completely normal and no treatment is required.

If the spots are seen in rows around the base of the head of the penis (also known as the glans), they are called 'coronal papillae' which are similar in appearance and again need no treatment. The best thing to do if you find these little white lumps is to not worry, don't pick or squeeze them and to maintain good hygiene by regular washing.

The advice above applies mainly to the situation where unprotected sex has not occurred. This is because 'genital warts', a sexually transmitted disease, can initially look similar to the 'normal' lumps I've mentioned and therefore has to be considered as a possible diagnosis. Warts appear mainly on and around the head of the penis but can involve the shaft of the penis and scrotum. A similar viral infection called 'molluscum contagiosum' can produce similar flesh-coloured lumps up to 5mm on the penis and surrounding skin and it is usually spread by sexual contact. These infections should be seen and treated by your doctor or by a specialist at the local hospital.

The 'normal' lumps will cause no irritation, pain or inflammation but if you are worried about any new spots, ulcers, lumps or pain which develop in the penis or scrotum, you should get it checked out. (34)[/quote]
Did a quick search, and that seemed like it might be helpful. As always, asking your doctor could never hurt.