Day after oral sex with another man I've got red bumps back of throat, swollen tonsils with white dots. Strep was negative. Std? Hiv? Getting nervous

Get help. First ask your partner if he has an infection, genital or other that you may have caught. Then go to doctor as you may need antibiotics.
Possible STD. See your pcp, or go to a public health clinic for a complete workup, and treatment. They will also be asking you information on your partner, so that they can treat him too. You should always use condoms when unsure of your partner's sexual history to protect yourself.
Not STD. First, there is no std of the common twelve stds, that has these symptoms or that become symptomatic within 24 hours of exposure. Strep tests are notoriously false in this type of setting. You would be wise to get std tests if there was semen exchanged in the encounter, but not today. That would be way too soon. But, you can breathe easy tonight. This is not the story of an std infection.