Red bump / Pimple on Penis head

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Hi I have a red bump/Pimple on my Penis head. It is painless and often itches sometimes but not all the time. It is been here for more than a week now. I have been sexually active for the last three months, so I got tested for Syphilis but the test came negative. Now after more than a week another really small red spot is appearing on the right side of the penis head. Can anyone help me diagnose it. Thanks.

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