Toung discomfort after oral sex with another man with him ejaculating in my mouth.  red tastebuds...?

Trauma. Depending on the vigor during the oral sex, there can be redness due to "trauma". I would recommend abstaining from oral sex and see if your oral cavity improves.
Keep mouth clean. Make sure to be brushing twice daily, use a separate soft toothbrush for your tongue. Rinse with non-alcohol based mouthwashes as the alcohol-based ones may irritate the tongue more. Stick to a basic diet (no citrus, tomato sauce, etc) and nothing too salty/spicy to help it heal. May take at least 3 days for it to feel normal again.