After ejaculation my new partner washed his penis, couple mins later i tried to put a condom, realized it was inside out, then flipped it and had sex. how high are the chances of contracting std or any infections? regret doing so very much?

When used correctly and consistently every time you have sex, condoms have been shown to be 98% effective against the transmission of STDs. They prevent bodily fluids and skin/sore contamination. Since the condom came in contact with his skin/bodily fluids/sores, then your vaginal mucosa/hands, there may be some risk of spread. Talk to your regular Dr about testing for HIV/ gonorrhea/ syphilis.

It is good to use condoms, however, condoms do not prevent some of the STDs, e.g. HPV, herpes, LGV, syphilis and skin infections. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines

Condoms help but are not 100% effective against disease. Best is to know your partners disease status AND use a condom.