Help.. Pimple on penis shaft

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hi everyone. it's the second time this has happened. I don't know if its just a random pimple or an ingrown hair or something more serious like an std. it does not burn or itch. but it gets uncomfortable at times. I practice good hygiene. shave down there. shower twice a day. the last time i had any sexual contact was more than 5 months ago but protected. it's been there for 2 days now and really worrying me. please assist with your opinions.

i think its an ingrown hair from shaving they are quite common at the base of the penis as thats commonly were hair grows