PLEASE HELP ME !! HIGHLY CONFUSED!

Last sunday on the 29th i recieved oral sex from a prostitute. (no condom) Tuesday i noticed this pimple? open sore? I have no clue what to call it.. it has now been a full week and since sexual activity and this sore on my shaft has not went away, it looks exactly the same as it did when i first saw it, no pain, itching, or anything like that it just popped up... Ive looked up numerous STDs and the closest thing to this is chancroid, but it looks too small to be that. i need an accurate diagnosis on what this might be from you guys before i continue to freak out. Thanks!

Im sorry i mean i noticed it Wednesday

it could be herpes did the spot pop and leak water ?

no it literally show up like that and still look like that til this day

no itching or burning, its completely painless

Do you find what it was ?

no not yet, it still looks the same