Medium Red bumb appeared on the shaft of my penis

The bump is not too big but not small, nothing surrounding it and no previous history with anything like it, The bump is red and if squished lightly, a white dot can be seen. It has been there for a few weeks now, and I brushed it off as a simple pimple and that it will go away in a week, but it hasn't. My partner claims she is std clean and we have been having sex for awhile now, I don't know why it is appearing now, Please help!

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