Pimple On The Penis, Painful, Got It After Having Sex. Advice?

Hello, I found a pimple (bump) on my penis shaft around the base on its left side, from yesterday afternoon. It is look like a pimple on a face during puberty period but with a bit difference in shape, as the pimple s tip is not ready to let any fluid goes out. The pimple is pinkish and its tip is a bit whitish. It is painful when it gets touched. I had sex and during that my penis twisted a bit and I experienced pain for few seconds, but then I continued my sex and I noticed this pimple almost around a day after. the pimple size is almost around like a dull or a small bean. I found this picture online which I think is quite close to my problem: WWW.WWWW.WW Thank you for your advice in advance!