Put direct pressure on it with a clean sterile bandage until the bleeding stops. If it is deep, go to the hospital or doctor's office because cuts are at high risk for infection. If it's a small cut, keep direct pressure until the bleeding stops and then clean with alcohol before lightly wrapping in another fresh bandage.
I had some kinda funny responses to this, but really I appreciate you being helpful, so I didn’t want to poke fun. but on the other hand (duh duh tschh), I’ve gotten way more serious injuries than a cut thumb and was totally fine as far as handling it. but anyway thanks for being a helpful person.
(it stopped bleeding after like ~17 min, and while it’s pretty deep, it’s not bad enough to need stitches or any real irrigation)