Had sex 3 days ago pain while urinating small bumps inside vagina pain started day after sex std free but now i'm not sure ?

Could be herpes: so you should get to a doctor immediately. Especially if sex was unprotected. Also get checked for other std's.

UTI? STD? Warts?: Your pain and the "small bumps" are not an STD from the exposure the previous day. No infection symptoms can start in less than 1-2 days. And the only STD causing "bumps" is warts, which typically appear 3-12 months after catching HPV. Regardless of when caught, you might have urinary tract infection, yeast, HPV/warts, herpes, or other STD. Play it safe and see your doctor ASAP. Good luck!

STD ? : The only way to settle the question is to have yourself examined and screened for STD's, can't make a diagnosis with history alone, make sure you have hodd exam and screening